ELEMENTARYAPPLIED 
CHEMISTRY 


UC-NRLF 


LEWIS  B.ALLYN 


GIFT  OF 


AbmU 


ELEMENTARY 
APPLIED  CHEMISTRY 


BY 


LEWIS  B.  ALLYN 

DEPARTMENT   OF   CHEMISTRY,  STATE   NORMAL   SCHOOL 
WESTFIELD,  MASSACHUSETTS 


For  the  world  was  built  in  order 
And  the  atoms  march  in  tune." 
—  EMERSON 


GINN  AND  COMPANY 

BOSTON  •  NEW  YORK  -  CHICAGO  •  LONDON 


GIFT 


COPYRIGHT,  1912,  BY 
LEWIS  B.  ALLYN 


ALL   RIGHTS  RESERVED 
912.11 


nrpf. 


GINN  AND  COMPANY  •  PRO- 
PRIETORS •  BOSTON  •  U.S.A. 


PREFATORY  NOTE 

The  object  of  the  exercises  in  this  book  is  to  create  and 
to  foster  a  real  love  for  and  interest  in  the  great  science  of 
chemistry,  to  give  the  pupil  a  broader  outlook  on  life, 
and  to  cause  him  to  feel  that  he  is  a  factor  in  the  busy, 
living  world. 

These  experiments  and  tests  have  been  of  personal  value 
to  hundreds  of  earnest  students ;  possibly  they  may  be  of 
value  to  you.  If  you  know  of  some  one  who  would  profit 
by  the  information  you  may  receive,  pass  it  on. 


445101 


CONTENTS 

SECTION  PAGE 

I.    FILTRATION 1 

II.    ACIDS  AND  ALKALIS 5 

III.  ALKALIS  IN  TEXTILE  ANALYSIS 7 

IV.  ACIDS  AND  ALKALIS   IN  THE   QUALITATIVE   ANALYSIS  OF 

SOILS 9 

V.    DETECTION    OF    SOME    OF    THE    COMPOUNDS    PRESENT    IN 

PLANTS 13 

VI.    EXERCISES  WITH  STANDARD  SOLUTIONS 16 

VII.    SANITARY  ANALYSIS  OF  WATER 28 

VIII.    EXAMINATION  OF  BAKING  POWDER 35 

IX.    ANALYSIS  OF  MILK 41 

X.    EXAMINATION  OF  ICE   CREAM,  CHEESE,   AND  CONDENSED 

MILK 52 

XI.    DISTILLATION  EXPERIMENTS 54 

XII.    DETECTION  OF  COAL-TAR  DYE 76 

XIII.  IDENTIFICATION  OF  VEGETABLE  COLORS 79 

XIV.  RAFFIA  DYEING 81 

XV.    CHEMISTRY  OF  STAINS 88 

XVI.    EOOD  PRESERVATIVES 90 

XVII.    EXAMINATION  OF  TOOTH  POWDERS 95 

XVIII.    EXPERIMENTS  WITH  GLUCOSE 97 

XIX.    EXAMINATION  OF  HEADACHE  POWDERS 102 

XX.    TESTS  FOR  ARSENIC 105 

XXI.   METHOD  FOR  TESTING  PAINT  AND  OILS 109 

XXII.    DETERMINATION  OF  FOOD  VALUES 113 

XXIII.  TESTING  URINE 118 

XXIV.  SELECTED  EXERCISES 120 

INDEX 125 

vii 


SUGGESTIONS  TO  TEACHER  AND  PUPIL 

Be  sure  that  the  work  done  is  correct,  and  then  certify  it. 

The  use  of  blanks  similar  to  the  one  on  page  x  gives  a 
suggestion  of  importance  to  the  task  performed  and  is  con- 
ducive to  honest,  accurate  work,  and,  best  of  all,  to  a  regard 
for  the  truth. 

Much  time  will  be  saved  by  making  counterpoises  with 
stoppered  vials  and  fine  shot  for  beakers,  crucibles,  evap- 
orating dishes  and  specific-gravity  flasks.  Test  the  accuracy 
of  these  tares  occasionally. 

If  you  are  not  sure  of  a  reaction,  work  with  a  sample 
which  is  known  to  contain  the  substance  in  question.  For 
example,  if  the  odor  of  phenylcarbamine  is  unknown,  heat 
a  few  drops  of  commercial  anilin  with  5  cc.  of  stock  solution 
of  KOH.  Add  a  cubic  centimeter  of  chloroform,  agitate 
gently,  cool,  and  note  the  odor. 

Form  the  habit  of  using  a  pipette  instead  of  a  graduate 
whenever  special  accuracy  is  desired. 

Distilled  water  should  be  used  for  dilutions  and  solu- 
tions, especially  for  solutions  of  precision. 

Many  semifluid  substances  may  be  ashed  by  allowing 
the  flame  to  strike  the  surface  of  the  material,  meanwhile 
applying  a  gentle  heat  to  the  bottom  of  the  crucible. 

Save  products  -and  samples.  Bottle  and  label  them.  A 
collection  is  an  inspiration  and  an  incentive. 

Notebooks  should  be  illustrated  by  mounted  samples, 
cuts,  and  clippings  from  newspapers  and  magazines. 

ix 


ELEMENTARY  APPLIED  CHEMISTRY 
REPORT  OF  CHEMICAL  ANALYSIS 


Sample- 


Obtained  from. 


Manufactured  by_ 


Test                        

Coal-tar  dye               

Vegetable  colors   

C  ethyl      

Alcohol^ 
^methyl  

Mineral  matter  or  metals    .... 

Organic  compounds  (miscellaneous)  . 

Bases                      

Radicals  

Essential  oils    

Glucose 

Acetanilid  or  phenacetin 

Equation      

f  fraudulent  .... 

Adulteration  ^ 
t  injurious      .... 

Oualitv    . 

REMARKS 


I  hereby  certify  that  the  above  is  correct  to  the  best  of  my  knowledge. 

Name 

Date 19— 


SUGGESTIONS  TO  TEACHER  AND  PUPIL        xi 

Much  collateral  reading  should  be  encouraged.  The 
following  books  and  pamphlets  are  valuable: 

LEACH,  A.  E.   Food  Inspection  and  Analysis.  John  Wiley  &  Sons. 

WILEY,  H.  W.    Foods  and  their  Adulteration.  Blakiston. 

BLYTH,  A.  W.  Foods,  their  Composition  and  Analysis.  D.  Van 
Nostrand  Company. 

PEARSON.   Jensen's  Milk  Hygiene.   J.  B.  Lippincott. 

OLSEN,  J.  C.    Pure  Foods.    Ginn  and  Company. 

OLSEN,  J.  C.  Quantitative  Chemical  Analysis.  D.  Van  Nostrand 
Company. 

SNYDER.    Human  Foods.    The  Macmillan  Company. 

ALLEN,  A.  H.  Commercial  Organic  Analysis.  D.  Van  Nostrand 
Company. 

COHN.    Tests  and  Reagents.    John  Wiley  &  Sons. 

Bulletin  No.  107,  Bureau  of  Chemistry,  United  States  Department 
of  Agriculture. 


ELEMENTARY  APPLIED 
CHEMISTRY 


SECTION  I 

FILTRATION 

Application  to  Qualitative  and  Quantitative  Analysis  (2-Part 
Compound).  A  very  satisfactory  remedy  for  tonsillitis  is  a 
mixture  consisting  of  equal  parts  of  sulfur  and  powdered 
sugar.  This  is  a  recognized  specific,  and  at  one  time  was 
sold  as  a  patent  medicine  at  fifty  cents  per  ounce.  The 
instructor  should  prepare  a  quantity  of  the  specific,  varying 
the  proportions  slightly.  Pass  the  mixture  several  times 
through  a  fine  sieve. 

(a)  Qualitative  Work.  Place  a  spoonful  of  the  powder  in 
a  beaker.  Add  50  cc.  of  water,  boil,  and  filter.  Test  both 
filtrate  and  residue  in  any  way  you  choose.  Of  what  is  the 
powder  composed  ?  How  do  you  know  ? 

Copy  and  sign  the  following  statement : 

I  hereby  certify  that  a  mixture  called  Tonsillitis  Specific  and 
examined  by  me  contains 


Name. 
Date 


(b~)  Quantitative  Work.  Weigh  as  exactly  as  possible 
3  to  5  g.  of  the  specific  upon  a  carefully  balanced  filter 
paper.  Adjust  to  a  funnel  and  wash  with  repeated  portions 
of  hot  water  until  the  filtrate  ceases  to  darken  when  a  few 

l 


' APPLIED  CHEMISTRY 


drops  are  heated  with  strong  H2SO4 ;  or  until  a  drop  leaves 
no  dark-colored  residue  when  evaporated  upon  a  piece  of 
platinum  foil. 

Dry  the  residue  over  a  water  bath ;  remove  and  cool. 

Place  the  duplicate  filter  paper  in  the  opposite  scale  pan 
and  weigh  the  sulfur  directly.  Determine  the  weight  of 
the  sugar  by  difference. 

Copy  and  sign  the  following,  or  use  a  printed  blank : 

The  sample  of  Tonsillitis  Specific  as  analyzed  by  me  contains 

per  cent  sulfur, per  cent  sugar. 

I  hereby  certify  that  the  above  is  correct  to  the  best  of  my 

knowledge. 

Name 

Application  to  the  Analysis  of  a  3-Part  Compound.  (<r)  In- 
troduce a  definite  amount  of  gunpowder  (2  to  3  g.)  into  a 
balanced  filter  paper.  Wash  with  repeated  portions  of  hot 
water.  Test  the  filtrate  for  residue  with  the  platinum  foil  as 
before,  using  only  a  drop  or  so  for  the  test.  Collect  the  filtrate 
and  evaporate  it  to  dryness  in  a  tared  evaporating  dish. 

(6)  Dry  the  residue  remaining  in  the  filter  paper.  Ex- 
tinguish all  flame  in  the  vicinity,  and  wash  the  residue  with 
three  or  four  10-cc.  portions  of  CS2.  Collect  filtrate  No.  2 
in  a  small  beaker.  Blow  on  it  gently  through  a  pointed 
tube  until  evaporation  is  complete,  or  allow  it  to  evaporate 
spontaneously.  What  remains  ? 

Dry  the  black  residue  over  a  water  bath  and  weigh  with 
the  counterpoised  filter. 

Record  and  certify  your  results. 

Character  and  per  cent  of  the  white  salt    .     .     .     

Character  and  per  cent  of  the  black  residue    .     .     

Character  and  per  cent  of  the  yellow  substance  .     

Read  on  the  history  and  composition  of  gunpowder. 


FILTRATION  3 

Application  to  Quantitative  Analysis  of  Soil.  Thoroughly 
dry  about  5  g.  of  soil  procured  by  the  pupil.  Weigh 
exactly  upon  a  balanced  and  folded  filter  paper.  Place  in 
a  funnel  and  wash  with  successive  portions  of  hot  water 
until  the  filtrate  does  not  darken  when  heated  with  an 
equal  volume  of  concentrated  H2SO4.  Dry  the  filter  paper 
and  contents  at  100°  C.  Reweigli  and  calculate  the  loss  of 
weight  as  soluble  matter.  Transfer  the  dried  residue  to  a 
counterpoised  porcelain  or  quartz  crucible  and  determine 
its  exact  weight.  Gently  heat  to  full  redness  with  occa- 
sional stirring,  being  careful  not  to  lose  any  of  the  material. 
Continue  heating  until  all  of  the  organic  matter  is  burned 
away.  Cool  the  crucible  in  a  desiccator  and  weigh  the  resi- 
due. Calculate  the  loss  as  insoluble  organic  matter. 

Tabulate  as  follows  : 

Soluble  matter % 

Insoluble  organic  mutter % 

Mineral  matter  % 


Total 100% 

I  low  have  you  seen  nitration  employed  outside  of  .school? 

What  is  another  name  for  the  process? 

What  kind  of  substances  may  be  separated  by  nitration? 

Make  a  list  of  mixtures  containing  such  substances. 

Application  to  Commercial  Analysis  of  Tea.  The  approxi- 
mate value  of  tea  may  be  determined  by  calculating  the  per 
cent  of  matter  which  is  not  soluble  in  hot  water.  The  in- 
soluble matter  should  not  be  in  excess  of  60  per  cent.  If 
over  this  amount,  the  presence  of  spent  or  exhausted  leaves 
is  indicated. 

Place  exactly  2  g.  of  the  finely  powdered  tea  in  a  balanced 
and  folded  filter  paper.  Extract  with  successive  portions  of 
boiling  water  until  the  filtrate  runs  clear.  Dry  the  residue 


4  ELEMENTARY  APPLIED  CHEMISTRY 

at  100°  C.    Cool  and  re  weigh.    Calculate  by  difference  in 
weight  the  per  cent  of  water-soluble  matter. 

Test  samples  of  tea  of  various  prices,  and  answer  the 
question,  Does  the  price  indicate  the  quality  of  tea  based 
upon  matter  insoluble  in  boiling  water  ? 

What  per  cent  of  insoluble  matter  has  the  tea  which  is 
used  at  your  home  ? 

To  isolate  Theine,  the  Alkaloid  of  Tea.  Extract  a  spoon- 
ful of  high-grade  tea  in  50  cc.  of  boiling  water.  Filter  the 
liquid  and  add  10  cc.  of  chloroform.  Transfer  the  mixture 
to  a  separatory  funnel,  shake  the  contents  vigorously  for  a 
minute,  and  allow  the  chloroform  to  settle.  Draw  it  off 
into  a  clean,  dry  watch  glass  and  allow  it  to  evaporate  at 
room  temperature.  Note  the  white,  silky  crystals  and  the 
pleasant  odor  of  the  theine. 

Repeat  the  above  experiment,  substituting  coffee  for 
tea.  The  alkaloid  of  coffee  is  called  what  ?  It  is  identical 
with  that  of  tea.  Its  chemical  symbol  is  C8H10N4O2  +  H2O. 
What  per  cent  of  nitrogen  does  it  contain  ? 

Application  to  a  Domestic  Analysis  of  Oysters.  The  de- 
termination of  the  amount  of  water  added  to  shucked  oys- 
ters is  important  from  the  viewpoint  of  the  consumer.  The 
per  cent  of  water  that  may  be  separated  by  means  of  a 
strainer  or  sieve  should  not  exceed  15  per  cent.1  Weigh 
on  a  trip  balance  about  a  pint  of  the  sample  as  purchased. 
Place  in  a  flat-bottomed  sieve  and  allow  to  drain  into  a 
weighed  dish  for  twenty  minutes,  stirring  gently  from  time 
to  time.  Determine  the  weight  and  per  cent  of  the  exterior 
liquor.  Determine  the  weight  and  per  cent  of  the  drained 
oysters  by  difference. 

1  Merck's  Report,  July,  1910,  p.  189. 


SECTION  II 
ACIDS  AND  ALKALIS 

Detection  in  Everyday  Compounds.  The  instructor  will 
show  samples  of  acids  in  solid,  liquid,  and  gaseous  form,  to 
do  away  with  the  impression  that  all  acids  are  liquids. 

Show  samples  of  the  common  alkalis. 

Discover  the  effect  of  acids  and  alkalis  upon  the  vari- 
ous indicators  —  phenolphthalein,  methyl  orange,  cochineal, 
carmine,  and  litmus. 

Take  home  some  litmus  paper  cut  into  small  strips.  Test 
different  articles  —  foods  at  the  table,  substances  in  the 
kitchen,  laundry,  etc.  Be  sure  that  the  substance  tested,  if 
a  solid,  is  either  dissolved  in  water  or  well  moistened. 

One  pupil  tested  the  following :  cream  of  tartar,  ashes, 
salt,  milk,  apple  juice,  borax,  sugar,  baking  soda,  washing 
soda,  soap,  vinegar,  tea,  kerosene,  tooth  powder,  coffee, 
butter,  stomach  bitters. 

Arrange  your  results  in  three  columns,  thus : 

Acid  Alkaline  Neutral 

Give  the  chemical  names  and  symbols  of  as  many  of  the 
above  list  as  possible.  What  per  cent  of  the  foods  eaten 
during  the  day  were  acid  ?  alkaline  ?  neutral  ? 

Determine  the  reaction  of  the  soil  from  your  lawn  or 
garden.  What  advantage  is  it  to  know  this  reaction  ? 

Thoroughly  moisten  20  to  50  g.  of  the  soil  and  in- 
sert two  pieces  of  litmus  paper,  one  red,  the  other  blue. 

6 


6  ELEMENTARY  APPLIED  CHEMISTRY 

Allow  them  to  remain  undisturbed  for  an  hour  or  even 
overnight. 

What  would  you  suggest  as  a  suitable  dressing  for  an 
acid  or  "  sour  "  soil  ?  for  an  alkaline  one  ? 

What  plants  have  a  distinctly  acid  reaction  ?  Do  you 
know  of  any  fruits  which  are  not  acid  ?  Find  out  the  name 
of  the  acid  which  imparts  the  sour  taste  to  the  common 
sheep  sorrel  (Tlumex  acetosella),  apples,  oranges,  grapes, 
rhubarb,  etc.  What  acid  is  found  in  the  membranous  cov- 
ering of  nuts  ?  Mention  some  of  the  alkalis  which  are 
found  in  nature. 


SECTION  III 
ALKALIS  IN  TEXTILE  ANALYSIS 

Determination  of  the  Per  Cent  of  Wool  and  Cotton  in 
Fabrics.  Wool  is  soluble  in  a  solution  of  NaOH  or  KOH. 
Cotton  is  insoluble  in  this  reagent. 

Qualitative  Work.  Place  a  small  piece  of  the  sample  in 
a  test  tube  or  crucible.  Cover  with  20  per  cent  KOH 


FIG.  1.   Mixed  goods  heated  with  KOH,  showing  cotton  residue 

and  boil  for  two  or  three  minutes.  If  the  sample  en- 
tirely dissolves,  what  is  the  per  cent  of  wool  ?  Suppose  it 
partially  dissolves,  what  is  indicated  ?  Experiment  with 
bits  of  cotton,  wool,  and  mixed  goods  until  you  are 
familiar  with  the  action  of  the  caustic  solution  upon  these 
substances. 

Caution.  Take  great  care  that  none  of  the  hot  alkali 
comes  in  contact  with  the  flesh  or  clothing.  If  this  does 
happen,  apply  dilute  HC1  at  once. 

7 


8  ELEMENTARY  APPLIED  CHEMISTRY 

Quantitative  Work.  If  a  portion  of  the  cloth  dissolves,  cut 
a  second  sample  about  8  cm.  square.  Determine  the  exact 
weight.  Place  in  a  beaker  or  large  evaporating  dish  and 
cover  with  the  caustic  potash.  Boil  for  three  minutes,  or 
until  the  wool  is  dissolved.  Remove  the  cotton  residue,  tak- 
ing care  not  to  lose  any  detached  threads.  Rinse  thoroughly. 
Add  a  drop  of  phenolphthalein  and  sufficient  HC1  to  make 
slightly  acid.  Wash,  dry  at  100°  C.,  and  re  weigh.  Calcu- 
late the  per  cent  of  wool  and  cotton.  Devise  a  method  for 
testing  silk. 


SECTION  IV 

ACIDS  AND  ALKALIS  IN  THE  QUALITATIVE 
ANALYSIS  OF  SOILS 

The  appended  list  comprises  the  more  important  plant 
foods,  and  the  majority  of  them  can  be  easily  detected  in 
common  soil. 

Water  Sulfuric  acid  as  sulfates 

Lime  (CaCO3)  Hydrochloric  acid  as  chlorids 

Carbon  dioxid  Nitric  acid  as  nitrates 

Ferric  oxid  (Fe2O3)  Magnesia  (MgO) 

Soda  (Na2O)  Sand  (SiO2) 
Potash  (K2O) 

Calcium  Carbonate.  Place  10  g.  of  the  soil  in  a  test 
tube  and  add  2  cc.  of  HC1.  An  effervescence  indicates  the 
presence  of  a  carbonate.  This  effervescence  may  frequently 
be  heard  when  the  action  is  only  faintly  visible,  by  placing 
the  ear  near  the  mouth  of  the  test  tube. 

Add  enough  water  to  make  a  thin  paste  and  boil  for  about 
two  minutes.  Make  alkaline  with  ammonia,  and  filter.  Test 
the  clear  filtrate  with  an  equal  volume  of  (NH4)2C2O4.  A 
cloudiness  or  flocculent  precipitate,  which  forms  on  standing, 
indicates  the  presence  of  calcium. 

CaCO3  +  2  HC1  =  ? 
CaCla  +  (NH4)aCa04=? 

Ferric  Oxid.  First  Test.  Boil  4  g.  of  the  soil  with  10  cc. 
of  HC1  (5  parts  of  acid  and  an  equal  volume  of  water). 
Filter  and  test  half  of  the  filtrate  with  ammonia  added  in 

9 


10  ELEMENTARY  APPLIED  CHEMISTPvY 

excess.    A  reddish-brown,  flocculent  precipitate  assures  the 
presence  of  iron  in  the  sample  of  soil. 

Second  Test.  To  the  other  half  of  the  nitrate  add  a  few 
drops  of  potassium  sulfo-cyanide  (KCNS).  A  blood-red 
color  is  seen  if  ferric  oxid  is  present  in  the  original  soil. 
Test  further  by  adding  a  little  HgCl2  to  a  cubic  centimeter 
of  the  red  liquid.  The  color  should  be  destroyed.  Write  the 
reactions  which  take  place  in  the  first  and  second  tests. 

Soda  and  Potash.  Boil  50  g.  of  the  soil  in  an  equal 
volume,  of  water,  stirring  constantly.  Allow  the  undis- 
solved  matter  to  settle  and  decant  the  clear  liquid.  Evapo- 
rate this,  preferably  over  a  water  bath,  to  about  5  cc.  Clean 
a  platinum  wire  by  heating  until  it  gives  no  color  to  the 
blue  Bunsen  flame.  Dip  the  wire  into  the  concentrated 
filtrate  and  place  immediately  in  the  outer  flame.  A  yellow 
coloration  indicates  soda.  A  lilac  or  violet  color,  best  seen 
through  a  piece  of  cobalt-blue  glass,  indicates  potash. 

Sulfuric  Acid  as  Sulfates.  To  a  little  BaCl2  solution  add 
a  few  drops  of  the  filtrate  left  from  the  soda  and  potash 
experiment.  Boil.  A  precipitate  insoluble  in  acids  indi- 
cates the  presence  of  sulfates.  Write  the  reaction  between 
sodium  sulfate  and  barium  chlorid. 

Hydrochloric  Acid  as  Chlorids.  To  two  or  three  cubic 
centimeters  of  the  soda  filtrate  add  a  few  drops  of  AgNOg. 
Churn  the  contents  of  the  test  tube.  A  white,  curdy  precipi- 
tate soluble  in  ammonia  indicates  the  presence  of  chlorids 
in  the  soil. 

Since  other  substances  are  likely  to  precipitate  the  silver 
solution,  decant  or  filter  off  the  ammoniacal  solution  and  add 
an  excess  of  HC1.  If  a  second  precipitate  is  seen  or  a  decided 
milkiness  is  evident,  the  presence  of  chlorids  is  assured. 
NaCl  +  AgNO8  =  ? 


ACIDS  AND  ALKALIS 


11 


Nitric  Acid  as  Nitrates.  To  one  volume  of  the  soda- 
potash  filtrate  add  two  volumes  of  strong  H2SO4  free  from 
nitrates.  Allow  the  mixture  to  cool.  Incline  the  test  tube 
and  cautiously  add  a  few  drops  of  a  concentrated  solution 
of  FeSO4,  so  that  the  liquids  will  not  mix.  A  brownish 
ring  at  the  junction  of  the  two 
solutions  assures  the  presence 
of  nitrates. 

Phosphoric  Acid  as  Phos- 
phates. To  5  cc.  of  the  soda- 
potash  filtrate  add  a  few  drops 
of  ammonium  molybdate  in 
HNO3.  Warm  the  evaporating 
dish  gently.  The  presence  of 
phosphates  is  indicated  by  a 
lemon-yellow  color,  or,  if  there 
is  a  considerable  quantity  pres- 
ent, by  a  yellow  precipitate. 

Magnesia  (MgO).  Boil  25  g. 
of  the  soil  in  50  cc.  of  water  and 
10  cc.  of  HC1.  Filter  and  evap- 
orate the  filtrate  to  about  5  cc. 
Add  a  few  drops  of  NH4C1  and 

an  equal  volume   of  NH4OH.    FlG<2.  Soil  before  and  afterboil- 
If  a  precipitate  forms,  filter  and 
test  the  filtrate  with  HNa  PC) . 


ing  in  strong  HC1.   The  residue 
is  sand 


A  white  crystalline  precipitate  of  MgNH4PO4,  soluble  in 
acids,  assures  the  presence  of  magnesium  in  the  soil. 

Sand.  Wash  10  g.  of  the  soil  in  a  250-cc.  beaker  with 
a  small  stream  of  water,  stirring  constantly  until  all  the 
humus  is  washed  out.  Boil  the  residue  in  strong  HC1 
for  five  minutes.  Sand  is  the  principal  substance  left. 


12         .  ELEMENTARY  APPLIED  CHEMISTRY 

Examine  with  a  magnifying  glass.  What  material  do  you 
recognize  ?  Can  you  suggest  what  some  of  the  original 
rock  might  have  been  ?  How  could  you  make  this  experi- 
ment quantitative  ? 

Another  important  constituent  of  soils  is  organic  nitro- 
gen. Its  detection  and  determination  should  be  omitted 
until  the  pupil  is  familiar  with  the  Gunning  method  for 
nitrogen,  q.v. 


SECTION  V 

DETECTION  OF  SOME  OF  THE  COMPOUNDS 
PRESENT  IN  PLANTS 

By  far  the  greater  part  of  the  growing  plant  is  carbon 
and  water.  How  could  you  prove  this  ? 

This  list  comprises  other  compounds  present  in  plants 
and  vegetable  matter. 

Organic  nitrogen  Phosphates 

Chlorophyl  Sulfates 

Starch  Chlorids 

Potash  and  soda  Iron 

Manganese  (infrequently)  Silica 

Organic  Nitrogen.  Grind  a  small  handful  of  grass  or 
hay  through  a  meat  chopper.  Mix  with  an  equal  weight 
of  soda  lime  or  with  strong  KOH,  and  heat  gently  in  an 
Erlenmeyer  flask,  in  the  mouth  of  which  is  suspended  a 
strip  of  moist  red  litmus  paper.  The  ammonia  given  off 
will  turn  the  test  paper  blue  and  prove  the  presence  of 
organic  nitrogen. 

Chlorophyl.  Chlorophyl  is  the  green  coloring  matter 
common  to  growing  plants. 

Grind  a  handful  of  grass  or  green  leaves,  or  scrape  the 
green  layer  from  any  woody  stem.  Triturate  in  a  mortar 
with  enough  alcohol  to  cover  the  mass.  Decant  or  filter 
the  green  liquid.  Allow  the  alcohol  to  evaporate  spon- 
taneously. The  chlorophyl  remains  as  an  intensely  green 
substance. 

13 


14  ELEMENTARY  APPLIED  CHEMISTRY 

When  extracted  from  suitable  kinds  of  leaves,  as  spinach, 
parsley,  etc.,  the  chlorophyl  is  sometimes  used  for  color- 
ing confections,  jellies,  and  beverages.  Of  what  use  is 
chlorophyl  to  plants? 

Starch.  Grind  a  few  kernels  of  corn  or  any  kind  of 
grain ;  scrape  a  potato  or  bruise  any  kind  of  root.  Boil 
with  10  cc.  of  water.  Cool  the  contents  of  the  tube  and 
add  a  few  drops  of  iodin.  A  distinct  blue  coloration  is 
proof  of  the  presence  of  starch. 

Potash  and  Soda.  First  Test.  Place  a  handful  of  dried 
grass  in  a  white  enameled  pan  or  upon  a  porcelain  tile. 
Light  it  with  a  blazing  splint.  When  it  has  stopped  burn- 
ing collect  the  residue  in  a  porcelain  crucible.  Repeat  the 
experiment  several  times  until  the  crucible  is  half  full. 
Heat  until  the  contents  are  thoroughly  ashed.  Sometimes 
the  ash  will  be  greenish,  due  to  the  presence  of  manganese, 
but  more  frequently  it  will  be  white  or  light  brown.  Care 
must  be  exercised  lest  the  ash  fuse  to  the  crucible. 

Wash  the  ash  into  a  beaker  and  boil  in  25  cc.  of  water. 
Allow  the  undissolved  material  to  settle,  and  reserve.  Ex- 
amine the  clear  liquid  directly  for  potash  and  soda  by  the 
flame  test,  as  directed  for  the  analysis  of  soils.  If  the  results 
are  not  positive,  evaporate  10  cc.  of  the  liquid  to  dry  ness 
and  repeat  the  test.  Is  the  liquid  acid  or  alkaline  ? 

Second  Test.  Cut  the  bottom  from  a  quart  bottle  or  use 
a  glass  percolator.  Loosely  plug  the  neck  of  the  percolator 
with  absorbent  cotton.  Fill  about  two  thirds  full  of  sifted 
wood  ashes,  through  which  allow  half  a  liter  of  warm  water 
to  pass.  Collect  the  filtrate  in  a  large  evaporating  dish  or 
enameled  pan.  Evaporate  to  dryness,  but  do  not  char.  The 
grayish- white  substance  is  potash  and  soda,  or  the  "  lye  " 
used  in  the  early  settlements  for  making  soft  soap.  Dissolve 


COMPOUNDS  PRESENT  IN  PLANTS  15 

in  a  little  water  and  treat  with  phenolphthalein,  cochineal, 
or  litmus.  Apply  the  flame  test. 

Phosphates,  Sulfates,  and  Chlorids.  Separate  the  unused 
portion  of  the  liquid  obtained  in  the  first  or  second  test 
into  three  parts  and  apply  the  appropriate  tests,  as  directed 
under  soil  analysis. 

:  Iron.  Boil  the  residue  saved  from  the  undissolved  ash 
with  a  few  cubic  centimeters  of  HC1.  Decant  the  liquid 
and  test  for  iron  with  KCNS. 

Silica.  The  residue  from  the  iron  test  is  mainly  silica. 
Wash  with  water,  allow  to  settle,  decant  the  liquid,  and 
rub  the  grayish  material  with  the  rounded  end  of  a  glass 
rod.  A  distinct  scratching  sound  can  usually  be  heard. 

Tabulate  those  exercises  in  which  you  have  used  an  acid 
or  an  alkali  as  a  reagent.  In  which  of  these  tests  have  you 
found  an  acid  or  an  alkali  ? 


SECTION  VI 
EXERCISES  WITH  STANDARD  SOLUTIONS 

Titration  and  Standard  Solutions.  The  strength  of  many 
solutions  may  be  determined  with  great  accuracy  by  adding 
definite  volumes  of  other  solutions  of  known  strength,  which 
will  react  chemically  with  them.  The  process  is  known  as 
titration,  and  is  of  great  importance  in  chemical  analysis. 

The  added  solution  is  called  a  standard  solution.  It  is 
made  to  contain  an  accurately  determined  weight  of  chemical 
substance  in  a  definite  volume. 

A  standard  solution  which  contains  1  g.  of  replaceable 
hydrogen  per  liter  is  known  as  a  normal  solution.  Standard 
solutions  may  be  spoken  of  in  terms  of  normal  solutions,  as 
1/2, 1/10, 1/50,  etc.,  usually  written  N/2,  N/10,  N/50. 

The  amount  of  a  given  substance  to  be  dissolved  in  dis- 
tilled water  and  made  up  to  a  liter  will  vary  directly  as  its 
molecular  weight  and  inversely  as  the  number  of  replace- 
able hydrogen  atoms  represented  in  its  molecule.  Thus  a 
liter  of  normal  HC1  must  contain  36.5  g.  of  acid,  since  its 
molecular  weight  is  36.5  and  only  one  atom  of  replaceable 
hydrogen  is  present.  A  decinormal  solution  of  this  acid 
will  contain  3.65  g.  per  liter,  while  a  cubic  centimeter  will 
contain  0.00365  g. 

A  liter  of  normal  H2SO4  must  contain  49  g.  of  acid, 
since  its  molecular  weight  is  98,  and  2  atoms  of  replace- 
able hydrogen  are  present.  N/10  H2SO4  will  contain  4.9  g. 
per  liter. 

16 


EXEECISES  WITH  STANDABD  SOLUTIONS     17 

A  liter  of  normal  oxalic  acid  (H2C2O4  +  2  H2O)  must 
contain  63g.  of  acid,  since  its  molecular  weight  is  126  and 
it  contains  2  atoms  of  replaceable  hydrogen. 

To  prepare  a  liter  of  N/10  oxalic  acid,  weigh  exactly 
6.3  g.  of  acid  of  the  highest  purity,  which  has  not  lost  its 
water  of  crystallization,  and  transfer  to  a  liter  measuring 
flask.  Add  about  500  cc.  distilled  water  and  agitate  to  dis- 
solve the  acid.  This  done,  make  up  to  the  mark  on  the 
neck  with  more  distilled  water.  Turn  into  a  clean,  dry 
bottle  and  mix  thoroughly. 

A  cubic  centimeter  of  any  normal  acid  will  exactly  neu- 
tralize a  cubic  centimeter  of  any  normal  alkali.  A  liter  of 
normal  NaOH  must  contain  40  g.  of  the  hydrate,  since  its 
molecular  weight  is  40.  A  liter  of  normal  KOH  must  con- 
tain 56  g.  of  the  salt  because  its  molecular  weight  is  56. 

That  one  may  know  when  enough  of  a  standard  solution 
has  been  added  to  neutralize  or  to  complete  the  reaction,  it 
is  customary  to  employ  a  third  or  neutral  substance  called 
an  indicator.  Litmus,  phenolphthalein,  cochineal,  methyl 
orange,  potassium  chromate,  etc.  are  often  used. 

Phenolphthalein  is  a  good  general  indicator,  but  must 
not  be  employed  when  more  than  traces  of  CO2  are  present. 
To  prepare,  dissolve  1  g.  of  the  crystals  in  100  cc.  of  95  per 
cent  alcohol.  To  use,  add  two  or  three  drops  of  the  alco- 
holic solution  to  the  acid  or  to  the  alkaline  solution  under 
examination.  In  acid  or  in  neutral  solutions  phenolphthal- 
ein is  colorless,  but  the  smallest  excess  of  alkali  turns  it  a 
vivid  purple-red. 

To  prepare  a  liter  of  N/10  NaOH,  weigh  roughly  4  g. 
of  the  pure  hydrate,  transfer  to  a  liter  flask,  and  make  up 
to  the  liter  mark  with  distilled  water.  When  the  hydrate  has 
dissolved,  transfer  to  a  large  bottle  and  mix  thoroughly. 


18 


ELEMENTARY  APPLIED  CHEMISTRY 


The  solution  must  now  be  standardized  by  the  N/10  oxalic 
acid  previously  made. 

By  means  of  an  accurate  pipette  transfer  10  cc.  of  the 
NaOH  solution  to  a  beaker.  Add  two  or  three  drops  of 
phenolphthalein.  Set  the  beaker  on  a  white 
tile  or  sheet  of  white  paper  and  draw  into  it 
from  a  burette  just  enough  N/10  oxalic  acid 
so  that  the  last  drop  destroys  the  lingering 
trace  of  pink  in  the  alkali.  Note  carefully 
the  amount  of  acid  required. 

Suppose  12  cc.  are  used ;  the  alkali  is  too 
strong,  for  1  cc.  of  the  acid  must  neutral- 
ize 1  cc.  of  the  alkali.    Add  50  cc.  of  dis- 
tilled water  to  the  NaOH  solution,  mix  well, 
and   again  titrate  10  cc.    By  observing  the 
change    made    by  the  50  cc.  of   water    one 
may  easily  calculate  the  amount  of 
water  necessary  to  bring  the  alkaline 
solution    to   the    exact    tenth-normal 
strength. 

Suppose  only  8  cc.  of  the  acid  are 
required  to  neutralize  the  solution ; 
the  NaOH  is  too  weak.  Add  a  drop 
of  saturated  NaOH  solution,  mix  well, 
and  titrate  a  second  10-cc.  portion. 
The  requisite  amount  of  alkali  to  be 
added  may  be  calculated.  Thus  by 
adding  water  or  alkali  as  required,  an  exact  balance  may 
be  secured.  Work  for  perfect  standardization.1 

1  For  those  wishing  to  go  more  into  detail  with  volumetric  solu- 
tions, Olsen's  "Quantitative  Analysis"  (D.  Van  Nostrand  Co.)  will  be 
helpful. 


FIG.  3.    A  convenient 
type  of  burette 


EXERCISES  WITH  STANDARD  SOLUTIONS     19 
A  cubic  centimeter  of  N/10  NaOH  is  equal  to 

Acetic  acid  (HC2H3O2) 0.0060  g. 

Boric  acid  (H3BO3) 0.0062  g. 

Citric  acid  (H3C6H5O7,  H2O) 0070  g. 

Lactic  acid  (HC3H5O3) 0.0090  g. 

Malic  acid  (C4H6O5) 0.0067  g. 

Oxalic  acid  (H2C2O4,  2  H2O) 0.0063  g. 

Sulfuric  acid  (H2SO4) 0.0049  g. 

Tartaric  acid  (H2C4H4O6) 0.0188  g. 

Determine  the  Acidity  of  Oranges  or  Lemons  calculated 
as  Citric  Acid.  Weigh  or  counterpoise  a  small,  clean,  dry 
evaporating  dish.  In  this  place  2  to  3  g.  of  orange  juice 
free  from  pulp.  If  lemon  juice  is  used,  1.5  to  2  g.  is  suffi- 
cient. Add  two  or  three  drops  of  phenolphthalein  (^phe- 
nolphthalein,  1  g.;  alcohol,  100  cc.).  Fill  a  burette  to  the  zero 
mark  with  N/10  NaOH  or  take  any  other  convenient  mark 
as  zero.  Allow  this  standard  solution  to  drop  slowly  into 
the  fruit  juice  until  the  first  permanent  trace  of  pink  appears 
in  the  well-mixed  solution.  If,  after  standing  for  a  minute, 
the  pink  color  disappears,  add  another  drop  of  the  alkali. 
The  fruit  juice  has  been  titrated  with  N/10  alkali. 

CALCULATION 
1  cc.  of  N/10  NaOH  is  equivalent  to  0.007  g.  of  citric  acid. 

Suppose  the  weight  of  the  orange  juice  and  evaporating 

dish  is 15.82  g. 

Suppose  the  weight  of  the  evaporating  dish  is     ....  13.30 

Weight  of  the  orange  juice  is 2.52  g. 

Suppose  at  the  end  of  the  reaction  the  burette  reads    .     .     13.80  cc. 

Suppose  the  zero  point  was 10.50 

Number  of  cubic  centimeters  of  N/10  NaOH  used   .       3.3  cc. 

3.3  x  .007  =  .0231  g.  of  citric  acid  in  the  2.52  g.  of  juice.  There- 
fore citric  acid  is  present  to  the  extent  of  0.916  per  cent. 


20          ELEMENTAKY  APPLIED  CHEMISTRY 

Test  the  acidity  of  commercial  lime  and  lemon  juices. 
The  U.S.P.  requires  about  7  per  cent  of  citric  acid. 

Determine  the  Purity  of  Cream  of  Tartar.  Place  exactly 
half  a  gram  of  the  sample  in  a  clean  beaker  and  dissolve 
in  boiling  water.  Add  the  phenolphthalein  solution  as  in  the 
preceding  experiment  and  titrate  with  decinormal  NaOH. 
After  the  first  pink  color  appears,  heat  nearly  to  boiling. 
If  the  color  disappears,  add  another  drop  of  the  alkali. 
Half  a  gram  of  pure  cream  of  tartar  requires  approximately 
26.6  cc.  (26.595)  of  N/10  NaOH  to  neutralize  it. 

If  your  balance  is  sufficiently  accurate,  weigh  exactly 
0.188  g.  Dissolve  in  hot  water  and  titrate,  using  phenol- 
phthalein. If  pure,  it  will  require  10  cc.  of  the  N/10  alkali. 

Determine  the  Purity  of  Baking  Soda.  Every  cubic  cen- 
timeter of  N/10  baking  soda  must  contain  .0084  g.  of 
HNaCO3.  Why? 

Titrate  exactly  half  a  gram  of  the  sample  with  N/10  HC1, 
using  methyl  orange  as  an  indicator. 

How  many  cubic  centimeters  were  required  ?  Suppose  the 
sample  were  absolutely  pure,  how  many  cubic  centimeters 
of  the  N/10  acid  would  be  required  to  neutralize  it  ? 

What  is  the  per  cent  of  purity  ?  Write  the  reaction 
between  HC1  and  HNaCO3. 

Determine  the  Per  Cent  of  Lactic  Acid  in  Milk.  Fresh 
milk  should  not  contain  over  .2  per  cent  of  acid.  Cream 
for  the  best  butter  should  contain  from  .5  to  .65  per  cent. 

Into  a  clean  white  evaporating  dish  or  teacup  place  9  cc. 
of  milk  or  cream,  being  sure  to  rinse  the  graduate  into 
the  cup.  Titrate  with  N/10  NaOH,  using  phenolphthalein 
as  an  indicator.  Stir  the  contents  of  the  cup  frequently 
with  a  glass  rod.  The  rod  must  not  be  taken  from  the 
dish  lest  some  of  the  contents  be  lost.  Neither  must  alkali 


EXERCISES  WITH  STANDARD  SOLUTIONS      21 


from  the  burette  spatter  upon  it.  The  first  permanent  tint 
of  pink  in  the  milk  indicates  the  end  of  the  operation.  The 
color  should  remain  pink  after  one  minute. 

The  number  of  cubic  centimeters  of  the  standard  alkali 
used,  indicates  directly  in  tenths  of  one  per  cent  the  amount 
of  acid  present.  Thus : 

6  cc.  of  the  alkali  =  .6  per  cent  of  acid. 
9.3  cc.  of  alkali  =  .93  per  cent  of  acid. 

An  Exercise  in  testing  Vinegar.  "  Vinegar  is  formed  by  the 
action  of  an  organism  found  in  the  'mother'  of  vinegar  upon 
weak  alcoholic  solutions. 
This  organism  serves  in 
some  way  to  carry  the 
oxygen  of  the  air  to  the 
alcohol.  The  sour  taste  is 
'largely  due  to  acetic  acid  " 
(Remsen). 

The  following  equations 
illustrate  the  process  of  so- 
called  acetic  fermentation : 
CaH60+0=C2H40+H,0. 

alcohol 

CHO+0-HCHO. 


acetic  acid 


The  physical  and  chemi- 
cal examination  of  vinegar 


FIG.  4. 


(Magnified) 


Vinegar  eels.' 
(Wilson) 

is  full  of  interest.  Examine  a  few  drops  under  a  low- 
power  microscope  and  see  if  you  can  find  any  of  the  so- 
called  "  vinegar  eels."  They  are  best  seen  after  allowing 
a  large  test  tube  of  vinegar  to  remain  undisturbed  for 
several  hours.  The  eels  are  usually  near  the  surface  of 
the  liquid. 


22  ELEMENTARY  APPLIED  CHEMISTEY 

Total  Acidity.  Introduce  exactly  6  cc.  of  the  sample  into 
a  clean  beaker  and  set  upon  a  white  paper  or  tile  in  a  good 
light.  Titrate  with  N/10  NaOH,  using  phenolphthalein  as 
an  indicator. 

The  number  of  cubic  centimeters  of  the  decinormal  alkali 
used,  divided  by  10,  represents  the  per  cent  of  acetic  acid. 

CALCULATION 

Suppose  34.3  cc.  of  the  standard  alkali  are  required  to  neutralize 

34  3 
6  cc.  of  the  vinegar ;  then  — —  =  3.43  per  cent  of  acetic  acid. 

Proof.    1  cc.  of  N/10  NaOH  neutralizes  0.006  g.  of  acetic  acid. 

34.3  x  .006  =  0.2053  g.  of  acetic  acid. 

Therefore  6  g.  (or  6  cc.)of  vinegar  contain  3.43  per  cent  of  acetic  acid. 

The  acidity  of  pure  cider  vinegar  should  not  be  less 
than  4.5  per  cent. 

Total  Solids.  Weigh  exactly  10  g.  of  the  vinegar  into  a 
tared  crucible  or  evaporating  dish  and  evaporate  to  dryness 
for  two  hours.  Cool  in  a  desiccator,  weigh,  and  calculate 
the  per  cent  of  the  residue.  The  total  solids  should  not  fall 
below  2  per  cent  by  weight  if  the  sample  is  cider  vinegar. 

Ash.  Place  the  vessel  containing  the  total  solids  on  a 
suitable  triangle  and  burn  to  ash  at  a  low  red  heat.  Cool 
and  weigh. 

The  ash  should  not  be  less  than  0.25  per  cent.  Its  reac- 
tion to  litmus  should  be  distinctly  alkaline.  If  it  is  not, 
it  contains  some  mineral  acid  which  must  be  determined. 
Gather  some  of  the  ash  on  the  loop  of  a  clean  platinum 
wire  and  apply  the  flame  test.  View  through  the  cobalt- 
blue  glass  if  necessary.  What  base  is  present  ? 

Add  a  few  drops  of  10  per  cent  HC1.  What  radical 
is  evident?  In  the  ash  of  pure  cider  vinegar  potassium 
carbonate  is  prominent. 


EXERCISES  WITH  STANDARD  SOLUTIONS      23 

Ashby's  Test  for  Mineral  Acids.  Prepare  a  solution  of  log- 
wood by  dissolving  0.5  g.  of  the  extract  in  100  cc.  of  boiling 
water.  Place  one  drop  of  this  solution  on  the  bottom  of  an 
evaporating  dish  and  dry  over  a  water  bath.  To  the  dried 
residue  add  a  drop  of  vinegar  and  dry  again.  Pure  vinegar 
gives  a  yellow  stain.  Free  mineral  acids  color  the  residue  red. 

To  be  sure  of  the  Ashby  reaction,  it  is  well  to  add  a 
little  H2SO4  to  vinegar  of  known  purity  and  compare  the 
result  with  the  residue  under  examination. 

To  detect  Sulfuric  Acid  in  the  Presence  of  Natural  Sulfates 
of  the  Vinegar.  Evaporate  100  cc.  of  the  sample  to  one  tenth 
of  its  volume,  and  when  cold  add  50  cc.  of  alcohol.  Sulfuric 
acid  remains  in  solution  while  the  natural  sulfates  are  pre- 
cipitated. Dilute  the  solution  and  precipitate  the  H2SO4 
with  BaCl2.  Write  the  reaction. 

Detection  of  Caramel.  Caramel,  or  burned  sugar,  is  some- 
times used  to  make  the  vinegar  seem  stronger  than  it  really 
is,  or  to  make  it  resemble  cider  vinegar.  Shake  5  cc.  of  the 
sample  with  twice  its  volume  of  amyl  alcohol.  If  caramel 
is  present,  the  supernatant  layer  will  be  wholly  or  par- 
tially decolorized.  The  under  layer  will  be  a  deep  brown, 
depending  upon  the  amount  of  caramel  present. 

Detection  of  Coal-Tar  Dye.  Use  the  double-dyeing  process 
of  Sostegni  and  Carpentieri,  q.v. 

To  distinguish  Cider  Vinegar  from  Other  Vinegars.  Lyth- 
goe's  Method.  Prepare  lead  subacetate  solution  by  dissolv- 
ing 180  g.  of  lead  acetate  in  half  a  liter  of  water.  Add 
110  g.  of  PbO  and  make  up  to  1000  g.  with  water.  Agitate 
often  and  filter. 

To  25  cc.  of  the  vinegar  add  2.5  cc.  of  the  subacetate 
solution.  Shake  the  contents  of  the  tube.  The  precipitate 
should  be  copious  and  settle  out  in  a  few  minutes. 


24 


ELEMENTARY  APPLIED  CHEMISTEY 


For  comparative  results,  centrifuge  in  a  graduated  tube 
and  read  the  volume  of  the  precipitate.  The  amount 
present,  in  part  at  least,  indicates  the  value  of  the  vinegar. 

Unless  a  precipitate  is  formed  the 
sample  is  not  cider  vinegar. 

Determination  of  the  Approximate 
Acidity  or  Alkalinity  of  Soils.  Boil 
exactly  10  g.  of  thoroughly  dried 
soil  in  30  cc.  of  water.  Filter  and 
wash  the  residue  several  times  with 
small  portions  of  hot  water.  Add  the 
washings  to  the  filtrate  with  two  or 
three  drops  of  phenolphthalein.  If 
the  reaction  is  alkaline,  titrate  with 
N/10  oxalic  aeid  until  the  pink  color 
is  destroyed  by  addition  of  the  last 
drop. 

Hlf  the  reaction  is  acid,  titrate  with 
N/10  NaOH  until  the  first  tinge  of 
pink  appears. 

In  either  case  express  the  result 
as  the  number  of  cubic  centimeters  of 
the  N/10  solution  required  to  neu- 
tralize the  nitrate. 

Approximation  of  the  Purity  of 
Cocoa.  The  purity  of  cocoa  can,  in 
part  at  least,  be  determined  by  cal- 
culating the  per  cent  of  its  ash,  which  in  pure  samples 
seldom  exceeds  5.5  per  cent;  and  under  ordinary  condi- 
tions the  ash  from  each  gram  of  the  sample  will  require 
not  more  than  3.7  cc.  of  N/10  oxalic  acid  to  neutralize  it. 
If  possible,  test  samples  from  your  home. 


FIG.  6.   True  and  artifi- 
cial vinegar  treated  with 
lead  subacetate 

The  artificial  vinegar,  on 

the  right,  shows  little  or 

no  effect 


EXERCISES  WITH  STANDARD  SOLUTIONS     25 

Burn  2  g.  of  the  sample  to  a  carbon-free  ash  at  the 
lowest  possible  heat.  Cool  the  crucible  and  calculate  the 
per  cent  of  ash.  Boil  the  contents  of  the  crucible  in  50  cc. 
of  water,  being  sure  to  rinse  it  well  and  save  the  washings. 
Titrate  with  N/10  oxalic  acid,  using  phenolphthalein  as 
an  indicator. 

Analysis  of  Soap.  Insoluble  Matter.  Dissolve  5  g.  of  the 
sample  in  75  cc.  of  water,  heating  if  necessary.  If  there 
are  more  than  mere  traces  of  residue,  filter  on  a  tared  filter 
paper,  wash  with  hot  water  until  the  filtrate  is  neutral,  dry 
at  105°  C.,  and  calculate  the  per  cent. 

Test  various  "  hand  "  and  scouring  soaps  for  insoluble 
matter. 

Alkali  may  exist  in  soap  in  at  least  three  forms,  —  free, 
combined,  and  as  alkaline  carbonates,  borates,  etc. 

Detection  of  Free  Alkali.  Treat  the  freshly  cut  surface 
of  the  soap  with  a  few  drops  of  the  alcoholic  solution  of 
phenolphthalein.  If  no  red  color  appears,  it  may  be  assumed 
that  free  alkali  js  absent.  Take  great  care  that  no  water 
comes  in  contact  with  the  soap,  otherwise  the  results  may 
be  misleading. 

When  testing  washing  powders  for  free  alkali,  dissolve  a 
small  quantity  in  alcohol  and  add  the  phenolphthalein. 

Combined  Alkali.  If  free  alkali,  alkaline  carbonates,  bo- 
rates,  etc.  are  absent,  dissolve  a  gram  of  the  soap  in  20  cc. 
of  hot  water.  Treat  with  phenolphthalein.  A  red  color  is 
immediately  seen.  Why  ? 

Titrate  with  N/10  oxalic  acid.  Allow  the  acid  to  drop 
slowly  from  the  burette  until  the  last  drop  added  destroys  the 
pink  color.  Shake  or  stir  the  solution  frequently  during  the 
operation  and  be  sure  to  waste  none.  If  after  a  minute 
the  pink  color  reappears,  add  another  drop  of  the  acid. 


26  ELEMENTARY  APPLIED  CHEMISTRY 

Free  alkali  may  also  be  estimated  by  dissolving  it 
from  1  g.  of  the  soap  by  means  of  alcohol.  Filter,  wash 
with  alcohol,  and  titrate  as  for  combined  alkali.  Calcu- 
late as  NaOH. 

CALCULATION  FOR  FREE  OR  COMBINED  ALKALI 

1  cc.  of  N/10  oxalic  acid  neutralizes  1  cc.  of  N/10  NaOH,  or  0.004  g. 
of  NaOH.  Suppose  the  number  of  cubic  centimeters  of  acid  required 
is  4.75 ;  then  the  per  cent  of  alkali  present  is  4.75  x  .004  =  .019, 
or  1.9  per  cent. 

Write  the  reaction  between  oxalic  acid  and  sodium 
hydrate. 

Total  Alkali.  If  the  soap  is  free  from  sand  and  other 
mineral  matters,  burn  2  g.  to  ash  in  a  porcelain  or  quartz 
crucible.  Cool  and  wash  the  contents  into  50  cc.  of  water. 
Boil  and  titrate  with  N/10  oxalic  acid,  using  two  drops 
of  methyl  orange  as  an  indicator.  (Dissolve  1  g.  of  methyl 
orange  in  1  liter  of  water.) 

Express  the  result  as  the  acid  number  ;  that  is,  the  num- 
ber of  cubic  centimeters  of  decinormal  acid  necessary  to 
neutralize  the  alkali  in  1  g.  of  the  soap. 

Alkaline  Carbonates.  Place  5  g.  of  the  soap  in  an  Erlen- 
meyer  flask  and  add  20  cc.  of  alcohol.  Set  a  funnel  in  the 
neck  of  the  flask  to  act  as  a  reflux  condenser,  and  heat  on  a 
water  bath  for  ten  minutes.  Alkaline  carbonates  will  be  in 
the  residue.  Place  a  bit  of  this  residue  on  a  clean  platinum 
wire  and  apply  the  flame  test  for  sodium  and  potassium 
(see  under  Soil  Analysis).  Filter  the  alcohol  and  dis- 
solve the  residue  in  warm  water.  Add  a  few  drops  of 
dilute  HC1.  A  marked  effervescence  indicates  the  presence 
of  carbonates ;  whether  Na2COg  (washing  soda)  or  K2CO8 
(potash)  will  be  indicated  by  the  flame  test. 


EXERCISES  WITH  STANDARD  SOLUTIONS      27 


Berates.  Place  5  cc.  of  turmeric  tincture  in  a  watch 
glass.  Add  a  few  drops  of  the  soap  dissolved  in  water,  and 
acidify  slightly  with  dilute  HC1.  Evaporate  to  dryness  over 
a  water  bath.  The  presence  of  borates  is  indicated  by  the 
pronounced  reddening  of  the  dried  residue. 

Record  the  results  of  your  analysis  in  this  form : 


SAMPLE 

PER  CENT 
INSOLUBLE 
MATTER 

PER  CENT 
FREE  ALKALI 

PER  CENT 
COMBINED 
ALKALI 

CARBONATES 

BORATES 

SECTION  VII 
SANITARY  ANALYSIS  OF  WATER 

The  importance  of  wholesome  water  cannot  be  overesti- 
mated. Do  the  barns,  the  sinks,  the  outbuildings,  contami- 
nate the  supply  ?  Does  the  water  dissolve  poisonous  metals 
from  the  pipes  or  other  sources  ?  Is  the  water  hard  or  soft  ? 
All  these  questions  we  shall  be  able  to  answer. 

Clear,  sparkling,  odorless  water  may  be  totally  unfit  for 
domestic  purposes,  while  a  suspicious-looking  or  peculiar- 
smelling  sample  may  be  quite  harmless.  A  simple  chemical 
analysis  is  often  of  great  value,  except  in  the  detection 
of  specific  disease  germs,  when  an  intelligent  bacteriologi- 
cal examination  is  necessary.  The  analysis  in  this  case, 
however,  may  throw  much  light  upon  the  source  of  the 
contamination. 

Keep  carefully  tabulated  results  of  your  analyses.  You 
can  then  see  at  a  glance  how  the  water  varies  from  the 
normal. 

Sediment.  Allow  a  test  tube  or  conical  glass  full  of  the 
water  to  stand  overnight,  or  centrifuge  10  cc.  in  a  pointed 
tube.  If  any  sediment  falls,  decant  the  liquid  and  exam- 
ine the  deposit  under  a  microscope.  This  deposit  may  be 
divided  into  two  classes,  harmless  and  suspicious  matter: 
harmless  matter,  sand,  clay,  alga,  diatoms;  suspicious  matter, 
hair,  epithelial  scales,  bits  of  wool  and  cotton,  muscle  fibers,  etc. 

Filter  the  remainder  of  the  original  sample  before  making 
further  tests. 

28 


SANITARY  ANALYSIS  OF  WATER 


29 


Color.  Fill  a  clean  test  tube,  the  longer  the  better,  with 
the  water,  or  use  a  Nessler  tube.  Stand  it  on  a  white 
paper  or  tile,  facing  a  good  light.  Cover  the  back  of  the 
tube,  except  an  inch  at  the  bottom,  with  a  piece  of  white 
paper.  On  looking  down  through  the  tube  the  water  should 
be  perfectly  transparent,  or  show  only  a  faint  bluish  tinge. 
Pollution  is  indicated  by  tints 
of  green,  yellow,  or  brown. 

Odor.  Warm  about  250  cc. 
of  the  water  to  38°  C.  in  a 
corked  flask.  Shake,  remove 
the  stopper,  and  smell  the  con- 
tents. Pure  water  is  free  from 
odor.  The  odor  may  be  classi- 
fied as  earthy,  vegetable,  alka- 
line, putrid,  etc. 

A  putrid  odor  indicates  de- 
composing animal  or  vegetable 
matter.  If  much  polluted  by 
fresh  sewage,  the  odor  of  urine 
is  not  infrequent.  One  should 
note  that  many  waters  unfit  to 
drink  have  no  odor.  A  positive 
odor  teaches  volumes ;  a  nega- 
tive result  is  of  little  value. 

Total  Solids.    These  consist 
for  the  most  part  of  CaCO3,  MgSO4,  CaSO4  with  their 
chlorids  and  nitrates,  NaCl,  SiO2,  and  organic  matter. 

Evaporate  70  cc.  of  the  water  to  dryness  in  a  thin, 
counterpoised  evaporating  dish  over  a  water  or  steam  bath. 
Dry,  cool  in  a  desiccator,  and  weigh  as  milligrams.  Every 
milligram  of  solids  per  70  cc.  represents  one  grain  per  gallon 


FIG.  6.    A  convenient  rack  for 
Nessler  tubes 

The  movable  mirror  shows  at  an 
angle 


30 


ELEMENTARY  APPLIED  CHEMISTRY 


in  the  original  sample.    Total  solids  in  good  water  may  be 
as  high  as  30  grains  per  gallon. 

Save  the  residue  and  examine  for  phosphates.    The  resi- 
due from  pure  water  is  almost  white.    Iron  gives  a  yellow 

or  coppery  luster  to  the  sides 
of  the  dish. 

Evaporate  about  50  cc.  of 
the  sample  in  a  porcelain 
evaporating  dish  and  heat 
gently  at  first.  Charring  de- 
notes the  presence  of  organic 
matter. 

Determination  of  ChloriaJes 
Measure  50  cc.  of  the  water 
with  a  pipette  into  each  of 
two  small  flasks  or  beakers. 
Add  three  or  four  drops 
of  potassium  chromate  solu- 
tion, 10  per  cent,  as  an  indi- 
cator, coloring  the  contents 
of  each  flask  exactly  alike. 
Place  both  flasks  on  a  white 
tile  in  a  good  light.  Titrate 
the  water  in  one  of  the  flasks 
with  a  standard  silver  solu- 
tion. Do  not  add  more  than  a  drop  at  a  time.  Continue 
the  titration  with  frequent  agitation  of  the  contents  until 
the  water  shows  the  first  tinge  of  red.  The  first  trace  is 
best  seen  by  looking  at  the  titrated  sample  through  the 
colored  water  in  the  control  flask. 

The  number  of  cubic  centimeters  of  the  silver  solution 
required  to  produce  the  red  tinge  equals  the  number  of 


FIG.  7.  Apparatus  for  the  determi- 
nation of  chlorin  in  water 
Control  flask  on  the  left 


SANITAEY  ANALYSIS  OF  WATEK  31 

parts  of  chlorin  in  100,000  parts  of  water.  If  the  water 
contains  more  than  five  parts  of  chlorin  per  100,000,  con- 
tamination from  human  urine  or  sink  drains  is  to  be  sus- 
pected, unless  the  water  is  taken  near  the  seacoast  or  from 
some  locality  where  the  normal  sodium  chloric!  content 
is  above  this  amount.  This  information  can  usually  be 
obtained  from  any  state  board  of  health. 

Write  the  reaction  between  silver  nitrate  and  potassium 
chromate. 

The  standard  silver  solution  is  prepared  by  dissolving  2.3944  g.  of 
pure  AgNO3  in  a  liter  of  distilled  water.  Keep  this  solution  in  a 
yellow  or  black  bottle  away  from  the  light. 


Detection  of  Ammonia.   To-gOTcc.  of  the  water  in  a  Nesslei 
tube,  tall  test  tube,  or  foot  tube,  adcljjfcc.  of  Nessler's^ 
reagent  and   note   the   color.    A   faint  yellow   tinge   only 
should  be   visible.    A  deeper  color  or  turbidity  indicates 
animal  contamination. 

Compare  the  treated  water  with  an  equal  volume  of  the 
untreated  sample  in  a  similar  tube. 

The  experiment  may  be  made  quantitative  by  comparing 
the  color  of  the  sample  with  different  Nesslerizec!  samples  of 
distilled  water  which  contain  known  quantities  of  NH4C1. 

All  natural  waters  contain  a  trace  of  ammonia,  but  the 
amount  present  should  not  be  sufficient  to  cause  more  than 
a  slight  coloration  with  the  Nessler  solution.  An  excep- 
tion must  be  made  in  the  case  of  rain  water,  which,  although 
relatively  pure,  contains  a  considerable  amount  of  ammonia 
dissolved  from  the  atmosphere.  Rain  water,  however,  shows 
practically  no  nitrates  or  chlorin. 

Nessler's  Reagent.  Dissolve  62.5  g.  of  KI  in  250  cc.  of  water.  Re- 
serve about  10  cc.  of  this  solution.  Run  into  the  remainder  a  cold, 
saturated  solution  of  HgCla  until  a  permanent  precipitate  forms. 


32  ELEMENTARY  APPLIED  CHEMISTRY 

Redissolve  this  precipitate  by  means  of  the  reserve  KI  solution. 
Very  cautiously  add  more  of  the  mercuric  chlorid  solution  until  a 
slight  precipitate  remains  after  agitation.  Add  150  g.  of  KOH  in 
water  and  make  up  to  a  liter. 

Allow  the  precipitate  to  settle  and  decant  or  siphon  off  the  clear 
liquid.  This  solution  improves  with  age. 

Detection  of  Nitrites.  Into  a  Nessler  tube  place  a  drop  of 
HC1,  2  cc.  of  sulfanilic  acid,  an  equal  volume  of  naphthyl- 
amine  hydrochlorid,  and  50  cc.  of  the  water  under  exami- 
nation. If  a  red  color  is  produced  immediately  or  within 
twenty  minutes,  the  presence  of  nitrites  is  assured. 

As  a  rule  nitrites  are  never  found  in  good  water. 

Sulfanilic  Solution.  Dissolve  0.8  g.  of  the  acid  in  100  cc.  of  pure 
water,  heating  if  necessary. 

Naphthylamine  Hydrochlorid  Solution.  Dissolve  0.8  g.  of  the  salt 
in  100  cc.  of  hot  water  to  which  1  cc.  of  HC1  has  been  added.  Filter 
through  bone  black  or  add  bone  black  to  the  solution,  and  decant  as 
needed.  Keep  from  the  light. 

Detection  of  Nitrates.  Evaporate  100  cc.  of  the  sample 
to  dryness  in  a  white  evaporating  dish  over  a  water  or 
steam  bath.  Treat  with  1  cc.  of  phenol-sulfonic  acid,  stir- 
ring thoroughly.  Add  10  cc.  of  distilled  water  and  half 
as  much  NH4OH. 

In  the  presence  of  nitrates  the  characteristic  yellow  color 
of  the  ammonia  salt  of  nitrophenol-sulfonic  acid  is  formed. 

Nitrates  are  present  in  almost  all  natural  terrestrial  waters. 

Detection  of  Phosphates.  Evaporate  70  cc.  of  the  sample 
to  dryness  or  use  the  residue  from  the  determination  of  total 
solids.  Add  a  few  drops  of  ammonia  molybdate  in  nitric 
acid  and  warm  gently.  There  should  be  only  a  slight  lemon- 
yellow  coloration.  A  decided  yellow  coloration  indicates 
animal  pollution.  The  degree  of  intensity  is  sometimes 
recorded  as  traces,  heavy  traces,  and  very  heavy  traces. 


SANITARY  ANALYSIS  OF  WATER  33 

Ammonium  Molybdate  Solution.  Dissolve  15  g.  of  ammonium  molyb- 
date  in  100  cc.  of  water,  with  the  addition  of  a  little  ammonia  if  neces- 
sary. If  there  is  pronounced  turbidity,  filter  the  solution  and  pour  with 
constant  stirring  into  a  mixture  of  50  cc.  nitric  acid  and  an  equal  vol- 
ume of  water.  Allow  the  solution  to  stand  in  a  warm  place  for  several 
days  at  a  temperature  of  about  80°  F.  and  decant  the  clear  liquid. 

^-^yV^V^»V^T'C/Jv-*v-^^* 

Determination  of  AUflgrtog* '  Oxygen.  This  test  gives 
reliable  information  concerning  the  amount  of  organic 
contamination,  but  does  not  distinguish  between  that  of 
animal  and  vegetable  origin. 

If  more  than  one  grain  per  gallon  is  absorbed,  the  water 
is  probably  polluted. 

Preliminary  Test.  Fill  two  test  tubes  half  full,  one  with 
S&nted  water,  the  other  with  the  sample.  To  each  add  a 
drop  of  strong  H2SO4  and  sufficient  KMnO4  in  distilled 
water  to  color  each  a  very  light  purple,  as  nearly  alike 
as  possible.  Boil  the  contents  of  each  tube.  What  is  the 
action  of  organic  matter  on  KMnO4? 

Regular  Test.  Prepare  a  standard  solution  of  KMnO4, 
0.395  g.  per  liter,  and  keep  in  a  clean  well-stoppered  bottle. 

Place  exactly  70  cc.  of  the  water  to  be  examined  in  a 
clean  flask  and  add  ten  drops  of  10  per  cent  H2SO4.  Warm 
gently  and  add  the  standard  solution  from  a  burette,  drop 
by  drop,  shaking  the  flask  gently  after  the  addition  of  each 
drop.  As  soon  as  the  faintest  tinge  of  pink  appears,  warm 
the  flask  again  and  notice  whether  the  color  is  permanent. 
If  not,  add  another  drop.  The  first  permanent  tinge  of  pink 
indicates  the  end  of  the  operation. 

Limit  the  test  to  fifteen  minutes.  Use  an  ordinary  Bohe- 
mian flask. 

When  70  cc.  of  water  is  thus  titrated,  each  cubic  centi- 
meter of  the  permanganate  solution  represents  0.1  of  a  grain 
per  gallon.  Good  water  absorbs  less  than  a  grain  per  gallon. 


34  ELEMENTARY  APPLIED  CHEMISTRY 

Metallic  Compounds.  Lead.  Evaporate  100  cc.  of  the 
sample  to  20  cc.  and  add  a  few  drops  of  K2O2O7.  A  pre- 
cipitate of  chrome  yellow  assures  the  presence  of  lead. 

Iron  and  Copper.  Boil  2  g.  of  stearic  acid  for  five  minutes 
in  30  cc.  of  the  suspected  water.  Set  aside,  and  when 
cool  compare  its  color  with  a  sample  of  the  acid  that  has 
been  boiled  for  the  same  length  of  time  in  distilled  water. 
Examine  before  a  white  background.  Iron  salts  impart  a 
yellow  color.  If  traces  of  copper  are  present,  the  acid  will 
be  colored  a  bluish  green,  which  can  be  seen  even  before 
the  acid  has  solidified. 

Hardness.  Titrate  100  cc.  of  the  water  with  N/10  HC1, 
using  methyl  orange  or  erythrosin  as  an  indicator.  The 
number  of  cubic  centimeters  of  the  decinormal  acid  used, 
multiplied  by  50,  represents  the  number  of  parts  of  CaCO3 
per  million  parts  of  water.  Calculate  the  results  to  parts 
per  100,000.  Water  is  considered  "hard"  if  it  contains 
over  five  parts  of  CaCO8  per  100,000. 


SECTION  VIII 
EXAMINATION  OF  BAKING  POWDER 

All  baking  powders  leave  a  more  or  less  insoluble  resi- 
due in  the  food  which  they  are  used  to  leaven.  What  salts 
does  one  take  into  his  system  when  he  eats  cake  or  biscuit 
made  with  cream  of  tartar,  with  alum,  or  with  phosphate 
baking  powder  ?  The  following  reactions  are  of  interest : 


KINO  OF  BAKING  REACTIONS 

POWDEll 


Cream  of  tartar 


Alum 


Phosphate   .     . 


CO2  +  TT,O 

Potassium  bitartrate  Rochelle  salts 

K2A12(SO4)4  +  6  HNaC03  =  A12(OH)6  +  3Na2S04 

Burnt  alum  Glauber's  salts 


•H4Ca(P04)2  +  2  HNaC03  =  HCaP04  +  HNaP04 
Ca  +  2C0   +  2H0 


Determination  of  Carbon  Dioxid.  The  value  of  a  baking 
powder,  in  part  at  least,  depends  upon  the  amount  of  avail- 
able CO2  it  contains.  To  determine  this,  two  separate  tests 
are  necessary. 

Total  Carbon  Dioxid.  This  determination  consists  of  lib- 
erating the  CO2  from  a  weighed  amount  of  the  sample, 
passing  the  gas  through  caustic  potash,  and  ascertaining 
the  increase  in  weight.  Into  an  Erlenmeyer  flask  of  about 
150  cc.  capacity  weigh  exactly  2  g.  of  baking-powder. 
Fit  the  flask  with  a  dropping  funnel  and  a  delivery  tube 
inclined  upward  at  an  angle  of  about  20°.  To  the  free 

35 


36 


ELEMENTARY  APPLIED  CHEMISTRY 


end  of  the  delivery  tube  attach  a  drying  tube  filled  with 
granulated  CaCl2  previously  saturated  with  COa. 

Fill  a  set  of  Liebig  potash  bulbs  two  thirds  full  of  a 
solution  of  1  part  KOH  and  2  parts  water.  Determine 
the  exact  weight  of  the  prepared  bulbs  by  suspending  from 


FIG.  8.    Apparatus  for  the  determination  of  carbon  dioxid 

one  arm  of  the  balance.  This  done,  connect  the  inlet  of  the 
bulbs  with  the  free  end  of  the  drying  tube,  and  the  outer 
end  with  an  aspirator. 

Fill  the  dropping  funnel  half  full  of  HC1  (sp.  gr.  1.1). 

Place  a  small  drying  tube  filled  with  soda  lime  in  the 
mouth  of  the  funnel,  to  prevent  any  CO2  from  the  air 


EXAMINATION  OF  BAKING  POWDER          37 

being  drawn  into  the  potash  bulbs  when  the  aspirator  is 
in  operation. 

Open  the  funnel  slightly  and  allow  the  acid  to  drop  slowly 
upon  the  sample.  Adjust  the  aspirator  so  that  the  gas  will 
be  drawn  through  the  potash  bulbs  at  the  rate  of  about  two 
bubbles  per  second.  When  nearly  all  the  acid  has  been 
added,  heat  the  contents  of  the  generating  flask  to  boiling, 
until  the  water  begins  to  condense  in  the  delivery  tube. 

Aspirate  until  the  potash  bulbs  are  cool;  then  discon- 
nect and  reweigh.  The  increased  weight  is  due  to  total 
carbon  dioxid. 

Write  the  reaction  between  HC1  and  baking  soda.  Is  the 
absorption  of  CO2  by  KOH  due  to  physical  or  chemical 
change  ? 

Residual  Carbon  Dioxid.  Thoroughly  clean  the  apparatus 
used  in  the  determination  of  total  carbon  dioxid.  Intro- 
duce 2  g.  of  the  sample  into  the  generating  flask  and  add 
20  cc.  of  cold  water.  Allow  it  to  stand  for  twenty  minutes. 
Then  set  the  flask  into  a  tin  can  surrounded  by  boiling 
water  for  the  same  length  of  time.  Drive  off  the  last  traces 
of  gas  in  the  pasty  mixture  by  boiling  for  one  minute. 
Aspirate  until  the  air  is  thoroughly  changed.  At  this 
point  in  the  experiment  connect  the  apparatus  and  perform 
the  work  exactly  as  for  the  determination  of  total  carbon 
dioxid.  The  increase  of  weight  in  the  potash  bulbs  is  due 
to  the  residual  carbon  dioxid. 

Available  Carbon  Dioxid.  From  the  per  cent  of  total  carbon 
dioxid  subtract  the  per  cent  of  residual  carbon  dioxid. 

The  average  per  cent  of  available  carbon  dioxid  found  in 
the  three  principal  kinds  of  baking  powder  is  as  follows : 
cream  of  tartar,  12.58;  phosphate,  12.86;  alum,  8.10  (Bulle- 
tin No.  13,  United  States  Bureau  of  Chemistry). 


38  ELEMENTARY  APPLIED  CHEMISTRY 

Tests  for  Radicals  found  in  Baking  Powder.  Chlorids. 
Shake  2  to  4  g.  of  the  sample  with  25  cc.  of  cold  water. 
Filter.  This  constitutes  a  cold-water  extract.  To  5  cc.  of 
this  extract  add  a  few  drops  of  10  per  cent  AgNO3  solu- 
tion. If  a  precipitate  forms,  agitate  and  allow  it  to  settle. 
If  it  is  insoluble  in  hot  water,  but  dissolves  in  ammonia, 
the  presence  of  chlorids  is  indicated. 

AgNO3  +  XC1  -  ?      AgCl  +  NH4OH  =  ? 

Sulfates.   Treat  a  few  cubic  centimeters  of  the  cold-water 
extract  with  barium  chlorid  solution.   A  precipitate  insolu- 
ble in  acids  and  in  water  assures  the  presence  of  sulfates. 
XSO4  4-  BaCl2  =  ? 

Tartrates.  Dissolve  a  crystal  of  silver  nitrate  in  5  cc.  of 
water  and  add  two  drops  of  ammonia.  Add  1  cc.  of  the 
cold-water  extract  and  heat  gently.  If  tartrates  are  present, 
the  silver  will  be  deposited  as  a  beautiful  silver  mirror  on 
the  interior  of  the  tube. 

Carbonates.  To  a  gram  or  so  of  the  dry  baking  powder 
in  a  test  tube  add  a  few  drops  of  dilute  II Cl.  Hold  a  glass 
rod  wet  with  limewater  so  that  the  escaping  gas  will  come 
in  contact  with  it.  If  the  limewater  becomes  milky,  the 
presence  of  a  carbonate  is  assured. 

Write  the  reaction  between  hydrochloric  acid  and  bicar- 
bonate of  soda.  Write  the  reaction  between  carbon  dioxid 
and  limewater. 

Phosphates.  Add  a  few  drops  of  the  cold-water  extract  to 
a  cubic  centimeter  of  ammonium  molybdate  (NH4)2MoO4  in 
HNOg.  Heat  gently.  A  lemon-yellow  precipitate  indicates 
the  presence  of  phosphates. 

Phosphoric  acid  is  an  important  constituent  of  the  body. 
Its  presence  can  be  easily  demonstrated  by  experiment. 


L 

^Mal 


EXAMINATION  OF  BAKING  POWDER  39 

Burn  a  piece  of  bone  in  a  clear  fire  until  the  residue  is 
perfectly  white.  Powder  from  2  to  3  g.  of  this  and  dissolve 
in  HC1.  Dilute  the  solution  about  one  half  and  add  an  ex- 
cess of  ammonia.  A  white,  gelatinous  precipitate  of  calcium 
and  magnesium  phosphate  forms.  Filter,  and  to  the  filtrate 
add  ammonium  oxalate.  The  characteristic  precipitate  of 
CaC2O4  is  evident. 

What  other  radical  was  present  in  the  bone  ? 

Tests  for  Bases  found  in  Baking  Powder.  Calcium.  To  a 
test  tube  half  full  of  the  extract  add  a  few  drops  of  ammo- 
nium oxalate  (NH4)2C2O4.  A  precipitate  insoluble  in  acetic 
acid,  but  soluble  in  'hydrochloric  acid,  shows  the  presence 
of  calcium. 

Write  the  reaction  between  ammonium  oxalate  and  cal- 
cium acid  phosphate. 

Ammonia.  Boil  50  cc.  of  the  extract  with  25  cc.  of  10  per 
cent  NaOH.  Test  the  steam  with  red  litmus  paper.  Avoid 
touching  the  neck  of  the  flask  with  the  paper.  If  present, 
the  liberated  ammonia  will  turn  the  test  paper  blue. 

Write  the  reaction  between  ammonium  carbonate  and 
sodium  hydrate. 

Aluminium.  (  Thirty -first  Report  of  the  Massachusetts  State 
Board  of  Health.)  Burn  to  ash  about  2  g.  of  the  baking  pow- 
der in  a  crucible.  Extract  with  boiling  water,  and  filter. 
To  the  filtrate  add  sufficient  NH4C1  to  give  a  distinct  odor 
of  ammonia.  A  flocculent  precipitate  indicates  the  presence 
of  aluminium.  The  lower  grades  of  baking  powder  often 
contain  salts  of  aluminium  or  of  ammonium. 

Detection  of  Alum  in  Pastry  as  well  as  in  Baking  Powder. 

ake  a  tincture  of  logwood  by  digesting  5  g.  of  the  well- 
powdered  chips  in  100  cc.  of  alcohol.  Prepare  a  saturated 
solution  of  (NH4)2CO3. 


40  ELEMENTARY  APPLIED  CHEMISTRY 

Rub  5  g.  of  the  baking  powder,  cake,  cooky,  or  biscuit 
in  a  mortar  with  10  cc.  of  water.  Add  2  cc.  of  the  logwood 
mixture  and  an  equal  volume  of  the  ammonium  carbonate 
solution. 

If  alum  is  present,  the  color  changes  to  lavender  or  blue, 
and  does  not  disappear  on  boiling.  If  alum  is  not  present, 
the  color  varies  from  red  to  pink. 


SECTION  IX 
ANALYSIS  OF  MILK 

More  disease  and  fraud  enter  the  home  through  the  milk 
supply  than  through  any  other  article  of  food.  Chemistry 
is  of  untold  benefit  in  protecting  people  from  these  evils. 

What  is  the  quality  and  condition  of  the  milk  which  you 
are  using  at  home  ? 

Fat.  Examine  a  drop  of  milk  under  a  half -inch  objective 
and  note  the  collection  of  various-sized  fat  globules.  De- 
scribe their  appearance  and  arrangement.  The  fat  of  milk  is 


Prom  CLEAN  MILK  From  DIRTY  MILK 

COTTON  PLUGS  Prom  FILTERED  MILK. 


FIG.  9 

one  of  its  most  variable  constituents,  and  the  determination 
of  the  amount  present  is  of  importance. 

Determination  of  the  Per  Cent  of  Fat  by  the  Babcock 
Method.  This  method  consists  in  adding  strong  sulfuric  acid 
to  the  milk  to  dissolve  all  of  the  solids  except  the  fat,  which 
is  afterwards  separated  by  means  of  a  centrifugal  machine. 

Measure  exactly  17.6  cc.  of  the  milk  into  a  Babcock  bottle 
by  means  of  a  milk  pipette.  Add  exactly  17.5  cc.  of  H2SO4, 

41 


42     ELEMENTARY  APPLIED  CHEMISTRY 

specific  gravity  1.83  at  60°  F.,  inclining  the  bottle  so  that 
the  acid  will  run  in  slowly  and  wash  all  adhering  milk 
from  the  neck. 

Shake  with  a  rotary  motion  so  as  to  thoroughly  mix 
the  acid  and  milk.  Avoid  getting  curds  into  the  neck 
of  the  bottle. 

If  the  work  has  been  done  properly,  the  mixture  will  be 
a  dark  brown  color  and  very  hot.  Place  directly  into  a 
centrifuge,  arranging  the  bottle  so  that  the  rotating  head 


FIG.  10.    Hand  and  electric  centrifuges  for  milk  analysis  or  for 
sedimentation 

will  balance  properly.    If  the  machine  vibrates  badly,  the 
balance  is  not  correct,  and  it  must  be  adjusted. 

Centrifuge  for  five  minutes;  then  set  the  bottle  into  a 
pan  of  hot  water  and  add  sufficient  hot  water  to  bring  the 
fat  up  to  the  neck  of  the  bottle. 

*  Centrifuge  for  two  minutes  and  add  hot  water  sufficient 
to  bring  the  fat  opposite  the  graduated  scale. 

Centrifuge  for  one  minute  and  take  the  reading  in  tenths 
of  1  per  cent  directly  from  the  scale. 

A  pair  of  small  dividers  is  useful  for  determining  the 
length  of  the  fat  column.  This  determined,  place  one  leg  of 


ANALYSIS  OF  MILK 


43 


the  dividers  upon  zero  and  take  the  reading  from  the  oppo- 
site leg.  It  is  customary  to  take  the  distance  from  the 
bottom  of  the  fat  column  to  the  top  of  its  meniscus  as 
the  true  length. 

The  fat  in  milk  varies  from  2.2  per  cent  to  9.0  per 
cent.  The  United  States  standard  is  3.25  per  cent.  What 
is  the  standard  in  your 
state  ? 

Determination  of  Acid- 
ity. Test  both  with  red 
and  blue  litmus  paper. 
Perfectly  fresh  cow's  milk 
is  generally  alkaline.  It 
is  sometimes  amphoteric, 
that  is,  it  exhibits  the 
phenomenon  of  reacting 
alkaline  with  red  litmus 
and  acid  with  blue.  The 
acidity  increases  as  the 
milk  sugar  is  converted 
into  lactic  acid. 

For  quantitative  deter- 
mination of  lactic  acid, 
see  page  20. 

Specific  Gravity.  De- 
termine with  a  lactometer,  specific-gravity  flask,  or  West- 
phal  balance.  Milk  of  good  standard  quality  should  have 
a  specific  gravity  of  1.027-1.033  at  60°  F. 

Milk  whose  specific  gravity  varies  from  these  limits  is 
of  a  suspicious  character. 

Total  Solids,  by  Evaporation.    Heat  2  g.  of  milk  to  a  con- 
stant weight  in  a  counterpoised  dish  over  a  water  bath. 


FIG.  11.   Babcock  bottles  for  milk  and 
cream  with  dividers  to  facilitate  reading 


44  ELEMENTARY  APPLIED  CHEMISTRY 

The  residue  of  milk  must  not  be  heated 
over  100°  C.,  as  it  will  decompose  and 
lose  weight  almost  indefinitely.  If  prop- 
erly heated,  the  dried  residue  will  be  almost 
white. 

Total  Solids,  by  Richmond* s  Slide  Rule. 
This  method  is  by  far  the  more  conven- 
ient, and  accurate  enough  for  all  practical 
purposes. 

Take  the  temperature  of  the  milk  and 
the  lactometer  reading.  Set  this  reading  on  I  3 

the  slide  opposite  the  observed  temperature. 
The  corrected  reading  will  be  found  oppo- 
site 60  on  the  scale.  Call  this  reading  A.  I  .§ 

Place  the  arrow  at  the  right-hand  end  of 
the  slide,  opposite  the  per  cent  of  fat  found    | 
by  the  Babcock  method.    Find  A  on  the 
opposite  edge  of  the  slide.    It  will  coincide 
with  the  total  solids  in  the  milk. 

The  results  obtained  by  these  two  methods 
should  agree  closely. 

Total  solids  should  not  be  less  than  12.50 
per  cent. 

Tests  for  Foreign  Matter,  Dirt,  Hair,  etc. 
Some  of  the  most  disagreeable  as  well  as 
dangerous  kinds  of  foreign  matter  which1 
contaminate  the  milk  supply  enter  through 
the  carelessness  of  the  producer. 

Construct  a  percolator  by  cutting  the  bot- 
tom from  a  pint  bottle,  or  use  an  ordinary 
glass  percolator  employed  by  a  druggist. 
Insert  a  plug  of  clean  absorbent  cotton  in 


ANALYSIS  OF  MILK 


45 


the  neck  from  the  inside,  and  allow  a  half  pint  or  more  of 
the  well-shaken  milk  to  slowly  filter  through.  Remove  the 
plug  carefully  and  examine  (see  p.  41). 

Insoluble  matter,  if  present,  can  easily  be  seen.  Wash 
the  clean  end  of  the  plug  gently  with  cold  water.  Dry  and 
mount  on  cardboard  with  an  appro- 
priate inscription. 

Tests  for  Adulterants :  Artificial 
Colors.  Coloring  matter  is  some- 
times added  to  milk  to  give  it  a 
rich,  creamy  appearance.  The  prac- 
tice, if  not  absolutely  injurious,  is 
at  least  reprehensible.  Why  ? 

The  two  most  commonly  em- 
ployed colors  are  annatto  and  coal- 
tar  dye. 

Detection  of  Annatto.  Shake 
about  5  cc.  of  the  milk  with  twice 
its  volume  of  ether  in  a  large  test 
tube.  When  the  liquids  have  sepa- 
rated, pour  off  the  ether  extract. 
Evaporate  on  a  water  bath.  Make 
the  residue  alkaline  with  NaOH 
and  pour  011  a  small  wet  filter 
paper.  The  annatto  will  be  ab- 
sorbed by  the  pores  of  the  paper. 

Wash  off  the  fat  gently  with  slightly  warmed  water. 
Annatto  will  give  a  decided  orange  tone,  which  turns  to 
pink  when  treated  with  a  few  drops  of  stannous  chlorid. 

Detection  of  Coal-Tar  Dye.  To  10  cc.  of  the  milk  add 
an  equal  volume  of  HC1  and  mix  thoroughly.  A  pink 
coloration  indicates  the  presence  of  azo  orange. 


FIG.  13.    Percolating  milk, 

for  dirt  and  other  foreign 

matter 


46  ELEMENTARY  APPLIED  CHEMISTRY 

Tests  for  Adulterants :  Preservatives.  The  .preservatives 
most  commonly  employed  to  keep  milk  sweet  for  a  longer 
time  than  nature  intended  are  formaldehyde,  compounds 
of  boron  (borax  and  boric  acid),  sodium  bicarbonate,  and 
calcium  sucrate. 

Detection  of  Formaldehyde  (HCHO).  This  is  one  of  the 
most  poisonous  of  preservatives  found  in  foods,  and  when 
so  used  cannot  be  too  strongly  condemned. 

Leach's  Casein  Test.  First  Part.  To  10  cc.  of  pure  milk 
add  an  equal  volume  of  hydrochloric  acid,  containing  about 
1  per  cent  of  Fe2Cl6.  Use  an  evaporating  dish  or  casserole 
and  heat  slowly,  stirring  or  shaking  the  contents  constantly 
to  break  up  the  curd.  When  nearly  but  not  quite  boiling, 
remove  the  heat  and  note  the  color  of  the  treated  milk  when 
hot  and  when  cold. 

Second  Part.  To  50  cc.  of  water  add  1  cc.  of  HCHO 
and  mix  the  liquids  well.  Add  two  drops  of  this  dilute 
formaldehyde  to  10  cc.  of  pure  milk  and  perform  the  work 
as  directed  under  the  first  part. 

How  is  the  presence  of  formaldehyde  indicated?  I  low 
much  was  in  the  milk,  assuming  that  the  cubic  centimeter 
added  to  the  water  contained  40  per  cent  formaldehyde  ? 

The  work  under  the  first  and  second  parts  is' designed  to 
make  the  pupil  familiar  with  the  appearance  of  milk  which 
contains  and  which  does  not  contain  formaldehyde,  when 
the  samples  are  treated  with  hydrochloric  acid  containing 
a  small  percentage  of  ferric  chlorid. 

To  test  any  given  sample  of  milk,  proceed  as  directed 
under  the  first  part,  and  if  the  results  are  similar  to  those 
obtained  under  the  second  part,  the  presence  of  formalde- 
hyde is  indicated.  Both  this  and  the  following .  test  are 
exceedingly  delicate  and  the  results  are  thoroughly  reliable. 


ANALYSIS  OF  MILK  47 

Detection  of  ECHO  by  means  of  Hehner's  Ring.  To  25  vol- 
umes of  H2SO4  add  1  volume  of  ferric  chlorid  solution. 
Place  4  cc.  of  this  reagent  in  a  large  test  tube  and  carefully 
add  5  cc.  of  the  suspected  milk,  inclining  the  tube  so  that 
the  milk  shall  rest  upon  the  surface  of  the  acid.  In  the 
presence  of  formaldehyde  a  violet  ring  is  seen  at  the  contact 
of  the  two  liquids. 

Detection  of  Boron  Compounds.  First  Part.  Place  5  cc. 
of  pure  milk  in  a  watch  glass  and  acidulate  slightly  with 
10  per  cent  HC1.  Add  five  drops  of  turmeric  tincture  and 
evaporate  to  dryness  over  a  water  bath.  What  is  the 
appearance  of  pure  milk  thus  treated  ? 

Second  Part.  To  5  cc.  of  the  milk  add  a  drop  of  boric  acid 
or  borax  dissolved  in  a  little  water.  Transfer  to  a  watch  glass 
and  proceed  as  before.  Take  care  that  the  mixture  does  not 
char.  How  is  boron  indicated  ?  The  reaction  is  said  to  be 
sensitive  to  1  part  of  boric  acid  in  25,000  parts  of  milk.  The 
red  color  is  proportionate  to  the  amount  of  boron  present. 

Test  unknown  samples  of  milk,  performing  the  work  as 
outlined  under  the  first  part.  If  the  sample  of  milk  is  very 
rich,  or  if  cream  is  under  examination,  dilute  with  two  or 
three  volumes  of  water. 

Turmeric  Tincture,  U.S. P.  Digest  any  convenient  amount  of 
ground  turmeric  root  in  small  quantities  of  water,  discarding  the 
liquids.  Digest  the  dried  residue  with  six  times  its  weight  of  alcohol, 
and  filter. 

Detection  of  Bicarbonate  of  Soda.  The  ash  of  pure  milk 
shows  no  effervescence  with  HC1.  Burn  10  cc.  of  milk  to 
a  white  ash  in  a  porcelain  or  quartz  crucible  over  a  low 
flame.  Treat  the  ash  with  a  drop  of  10  per  cent  HC1.  An 
effervescence  indicates  bicarbonate  of  sodium. 

HNaC08+2HCl  =  ? 


48  ELEMENTARY  APPLIED  CHEMISTRY 

Detection  of  Calcium  Sucrate.  This  substance  is  used  as 
a  thickener  as  well  as  a  preservative,  and  is  more  frequently 
found  in  cream  than  in  milk.  It  may  be  readily  detected  by 
means  of  the  Baier  and  Neumann  test  which  follows : 

First  Part,  the  Sugar.  To  25  cc.  of  the  milk  or  cream  add 
10  cc.  of  a  5  per  cent  solution  of  uranium  acetate.  Shake 
and  allow  to  stand  for  five  minutes. 

Filter ;  if  the  filtrate  is  not  clear,  pour  it  through  again. 
To  10  cc.  of  the  clear  filtrate  (if  the  sample  is  cream, 
use  the  total  filtrate)  add  2  cc.  of  a  cold  saturated  solu- 
tion of  ammonium  molybdate  freshly  prepared  and  8  cc.  of 
dilute  HC1  (1  part  of  25  per  cent  HC1  and  8  parts  of 
water).  Agitate  the  mixture  well  and  place  the  small  flask 
containing  it  in  a  water  bath  at  80°  C.  for  ten  minutes. 

If  the  sample  is  pure,  the  solution  will  be  a  peculiar 
green,  resembling  nickel  sulfate  solution ;  but  if  sugar  is 
present,  it  will  be  a  Prussian  blue  color. 

Second  Part,  the  Calcium.  Evaporate  25  cc.  of  the  milk 
or  cream  to  dryness  and  burn  to  ash  in  a  muffle.  Dissolve 
the  ash  in  20  cc.  of  N/10  H2SO4.  Boil  to  expel  the  CO2  and 
titrate  back  with  N/10  NaOH,  using  phenolphthalein  as 
the  indicator. 

Express  the  results  as  cubic  centimeters  of  N/10  acid  re- 
quired to  neutralize  100  g.  of  milk  or  cream.  Suppose  that 
the  ash  was  dissolved  in  20  cc.  of  N/10  acid  and  that  14  cc. 
N/10  NaOH  neutralized  the  excess.  It  is  evident  that  6  cc.  of 
the  acid  was  required  to  neutralize  the  alkalinity  of  the  ash. 

Detection  of  Gelatin  in  Milk,  Cream,  and  Ice  Cream. 
This  substance  is  sometimes  used  in  cream,  and  more 
frequently  in  ice  cream,  either  as  a  thickener  or  to  make 
the  material  stand  transportation  better.  Gelatin  is  readily 
detected  by  the  Stokes  test. 


ANALYSIS  OF  MILK 


49 


Stokes's  Test.  To  10  cc.  of  the  sample  add  an  equal 
volume  of  acid  nitrate  of  mercury  solution  and  20  cc.  of 
cold  water.  Shake  the  mixture  vigorously  and  allow  it  to 
stand  for  five  minutes.  Filter;  if  gelatin  is  present,  the 
filtrate  will  be  opalescent.  Confirm  by  treating  the  filtrate 
with  1  cc.  of  a  saturated  aqueous  solution  of  picric  acid. 
The  gelatin  will  be  precipitated  as  a  yellow  solid,  more  or 
less  flocculent  in  appearance. 

Acid  Nitrate  of  Mercury  Solution.  Dissolve  any  convenient  weight 
of  mercury  in  twice  its  weight  of  concentrated  HNO3  and  dilute  this 
solution  to  25  times  its  bulk  with  water. 

Detection  of  Milk  adulterated  by  Skimming  and  by 
Watering.  In  order  to  do  this  work  intelligently  one  must 
become  familiar  with  the  principal  factors  employed  in 
calculations  of  this  kind.  These  factors  are: 

Total  solids :  all  the  constituents  of  milk  except  water. 

Fat. 

Solids  not  fat:  obtained  by  subtracting  the  fat  content 
from  the  total  solids. 

Proteins :  the  nitrogenous  part  of  the  milk. 

Ash :  the  mineral  constituents. 

Milk  sugar  and  lactose. 

The  following  table,  devised  by  H.  C.  Lythgoe,  is  believed 
to  show  the  limits  between  which  normal  milk  varies : 


Extreme  limits 
(per  cent) 

Usual  limits 
(per  cent) 

Herd  milk 
(per  cent) 

Total  solids                  .     . 

10  0—  17  0 

10  5—  16  0 

11  8—  15  0 

Fat  
Proteins   

2.2  -    9.0 
2.1  —    8.5 

2.8-    7.0 
25—    45 

3.2-    6.0 

25—    40 

Ash      .          .          ... 

06—    09 

0  7  —    08 

0  7  —    08 

Solids  not  fat     .... 
Milk  sugar    

7.5-  11.0 
4.0-    6.0 

7.7  -  10.0 
4.2-    5.5 

8.0-    9.5 
4.3-    5.3 

50  ELEMENTARY  APPLIED  CHEMISTRY 

A  relation  has  been  found  to  exist  between  the  fat  and 
proteins  of  milk.    If  the  fat  is  given,  the  proteins  may  be 
approximately  calculated  by  means  of  Van  Slyke's  formula : 
0.4  (F.- 3) +2.8  =  P. 

Suppose  the  fat  found  in  a  certain  sample  of  milk  is 
3.50  per  cent.  According  to  the  formula,  the  proteins  are 
3.0  per  cent. 

A  relation    also    exists   between    the    total    solids    and 
proteins,  which  is  expressed  by  Olsen  as 
T.S.-T.S/1.34  =  P. 

Suppose  the  solids  in  the  sample  mentioned  above  were 
12.50  per  cent.  The  proteins,  by  Olsen's  formula,  are  3.18 
per  cent.  If  the  milk  is  pure,  the  per  cent  of  proteins  calcu- 
lated by  the  two  formulas  will  agree  closely  with  a  variation 
of  approximately  0.2  per  cent  or  less.  If  the  milk  is  adulter- 
ated with  water  or  by  skimming,  the  results  will  not  agree, 
the  difference  increasing  with  the  amount  of  adulteration. 

Illustrations.  A  sample  of  milk  known  to  be  watered  contained 
3.4  per  cent  fat  and  10.41  per  cent  of  total  solids. 

Proteins  calculated  from  the  fat 2.96% 

Proteins  calculated  from  the  solids     ....     2.65% 
Difference 31% 

A  sample  of  milk  known  to  be  skimmed  contained  2  per  cent  fat 
and  11.18  per  cent  of  total  solids. 

Proteins  calculated  from  the  fat 2.40% 

Proteins  calculated  from  the  solids     ....     2.84% 
Difference 44% 

According  to  Lythgoe  we  may  use  these  formulas  in  the 
indirect  calculation  of  milk  sugar,  if  we  assume  the  average 
ash  of  milk  to  be  0.7  per  cent. 

T.S.  -  (F.  +  [0.4  (F.  -  3)  +  2.8]  +  0.7)  -  Milk  sugar. 
T.S.  -  (F.  +  [T.S.  -  T.S./1.34]  +  0.7)  =  Milk  sugar. 


ANALYSIS  OF  MILK  51 

Detection  of  Skimmed  Milk.  If  the  sample  has  been 
skimmed,  the  calculated  proteins  will  exceed  the  fat,  and 
the  calculated  milk  sugar  will  be  too  high,  exceeding  4.8 
per  cent,  which  is  approximately  the  average  milk  sugar, 
according  to  the  table. 

If  the  fat  is  less  than  2.2  per  cent  and  the  solids  not 
fat  are  above  8.5  per  cent,  the  milk  has  probably  been 
skimmed. 

Detection  of  Added  Water,  Copper  Sulfate  Method.  Since 
there  is  no  chemical  test  to  distinguish  between  added 
water  and  the  water  naturally  present  in  milk,  it  is  cus- 
tomary to  precipitate  the  fat  and  proteins  by  means  of 
acetic  acid,  copper  sulfate,  or  by  spontaneous  souring.  This 
leaves  the  fat  and  protein  in  the  curd,  the  milk  sugar  and 
ash  in  the  whey. 

Dissolve  72.5  grains  of  pure  crystallized  CuSO4  in  a  little  water 
and  dilute  to  1  liter.  Adjust  this  to  have  a  specific  gravity  of  1.0443 
at  20°  C.  compared  with  water  at  4°C. 

To  1  part  of  copper  solution  add  4  parts  of  sweet  milk, 
shake  thoroughly,  and  filter. 

If  the  specific  gravity  of  the  clear  filtrate  is  less  than 
1.0245  at  20°  C.,  compared  with  water  at  4°  C.,  added  water 
is  indicated. 

Dry  5  cc.  of  the  copper  serum  to  a  constant  weight  over 
a  water  bath.  Determine  the  weight  of  the  5  cc.  from  the 
specific  gravity  of  the  serum  and  calculate  the  total  solids. 
If  the  total  solids  are  below  5.28  per  cent,  added  water  is 
indicated. 


SECTION  X 

EXAMINATION  OF  ICE  CKEAM,  CHEESE,  AND 
CONDENSED  MILK 

Determination  of  the  Fat  in  Ice  Cream.  Tare  a  Babcock 
cream  bottle  and  add  10  g.  of  the  well-mixed  sample 
together  with  5  or  6  cc.  of  water.  Mix  thoroughly  and 
add  just  enough  sulfuric  acid  to  turn  the  contents  dark 
brown.  Avoid  an  excess  of  acid,  as  the  mixture  will  char 
badly.  Proceed  with  the  regular  Babcock  test.  Multiply 
the  scale  reading  by  18  and  divide  by  10,  to  find  the  per 
cent  of  fat. 

The  per  cent  of  fat  in  ordinary  cream  is  also  found  by 
this  method. 

Starch.  Boil  a  small  quantity  of  the  sample  in  a  test 
tube  with  10  cc.  of  water.  Cool,  and  add  a  few  drops  of 
iodin  tincture.  The  well-known  blue  color  will  be  evident 
if  the  sample  contains  starch. 

If  starch  is  present,  place  a  drop  of  the  sample  on  a 
slide  and  examine  with  the  microscope  to  see  if  you  can 
determine  the  kind. 

Gelatin.   Apply  Stokes's  test. 

Fat  in  Cheese.  Weigh  6g.  of  the  sample  in  a  tared  beaker. 
Add  10  cc.  of  boiling  water  and  a  few  drops  of  ammonia. 
Stir  gently  until  a  smooth  emulsion  is  formed.  Transfer 
the  contents  to  a  Babcock  cream  bottle,  cool  slightly,  and 
add  17.6  cc.  of  H2SO4,  first  rinsing  out  the  beaker  with  the 
acid.  Proceed  with  the  regular  Babcock  test. 

62 


ICE  CKEAM,  CHEESE,  CONDENSED  MILK       58 

The  fat  reading  on  the  scale  multiplied  by  18  and  divided 
by  the  weight  of  the  sample  (6  g.)  gives  the  per  cent  of 
fat  in  the  cheese. 

How  can  you  distinguish  a  full-cream  cheese  from  a 
skimmed-milk  cheese  ? 

Fat  in  Condensed  Milk  (Unsweetened).  Weigh  6  g.  of 
the  thoroughly  mixed  sample  into  a  tared  Babcock  milk 
bottle  and  add  enough  water  to  make  the  volume  up  to 
about  17.6  cc.  Mix,  and  add  sufficient  H2SO4  to  produce  the 
deep  brown  color  required  by  the  Babcock  method.  About 
14  cc.  of  acid  will  be  needed.  Proceed  with  the  regular 
Babcock  test. 

Multiply  the  fat  reading  by  3,  to  find  the  correct  per 
cent  of  fat  in  the  sample. 

Number  of  Times  Condensed  and  Fat  in  the  Original  Milk. 
The  average  ash  of  pure  milk  is  .70  per  cent.  Burn  from 
2  to  3  g.  of  the  sample  in  a  crucible  and  calculate  the  per 
cent  of  ash.  This  per  cent  divided  by  .7  gives  approximately 
the  number  of  times  the  milk  has  been  condensed. 

Divide  the  fat  found  by  the  Babcock  method  by  the 
number  of  times  condensed,  to  find  the  fat  in  the  original 
sample. 


SECTION  XI 
DISTILLATION  EXPERIMENTS 

Prepare  a  solution  of  2  g.  of  NaCl  in  50  cc.  of  water. 
Taste.  Add  a  few  cloves  and  a  little  sand,  and  color  with 
red  ink  or  dye.  Pour  into  a  retort  or  distilling  flask.  Adjust 
a  suitable  condenser  and  distil  off  about  one  half. 

Examine  both  residue  and  distillate.  What  substances 
are  present  in  the  distillate  that  were  present  in  the  original 
mixture  ?  What  kinds  of  substances  are  separated  by  distil- 
lation ?  What  physical  principle  is  involved  ?  What  prac- 
tical applications  of  distillation  do  you  know  of  ?  What  is 
fractional  distillation  ? 

Extraction  of  Essential  Oils.  The  odor  and  taste  of  many 
vegetable  substances  is  due,  in  large  measure,  to  the  presence 
of  a  volatile  compound  known  as  essential  oil. 

What  is  the  difference  between  fixed  and  essential  oils  ? 

Extract  the  essential  oil  from  wintergreen  leaves,  sweet 
birch  (Eetula  lentulci),  cloves,  cinnamon,  nutmeg,  pepper- 
mint, bay  leaves,  orange  or  lemon  rind. 

To  obtain  the  greatest  amount  of  oil  from  any  of  these 
substances,  grind  through  a  meat  chopper,  add  water  to 
make  an  extremely  thin  paste,  and  distil.  At  first  the  dis- 
tillate will  be  of  a  milky  appearance,  due  to  the  suspended 
oil.  Set  aside  until  the  liquid  clears. 

A  second  method  for  the  extraction  of  essential  oils, 
which  gives  even  better  results  than  the  first  and  removes 
the  liability  of  breaking  the  retort  through  the  heavy 

54 


DISTILLATION  EXPERIMENTS  55 

material  sticking  to  the  bottom,  is  to  place  the  finely  ground 
mass  in  a  dry  flask  fitted  with  a  two-hole  stopper  and  con- 
nected with  a  condenser.  Steam  from  a  generating  flask  is 
blown  in  through  a  long  bent  glass  delivery  tube,  which 
extends  nearly  to  the  bottom  of  the  flask. 

What  is  the  use  of  essential  oils  ?  What  is  the  meaning 
of  "  essence,"  "  extract,"  and  "  tincture  "  ?  How  may  essen- 
tial oils  be  extracted  except  by  distillation  ?  (See  Harpers' 
Monthly  for  November,  1906.) 

Experiments  with  Alcohol.  Few  substances  are  of  greater 
industrial  value  than  alcohol.  Make  a  list  of  the  uses  of 
alcohol,  either  ethyl  (C2H5OH)  or  methyl  (CH3OH),  or 
both.  What  is  denatured  alcohol  ? 

Usually  from  5  to  8  per  cent  of  grain  alcohol  is  sufficient 
to  preserve  the  extractive  principles  of  medicine.  How  do 
you  account  for  such  high  amounts  as  28  to  44  per  cent 
sometimes  present  ? 

Make  a  medicine  tester.  Cut  a  piece  of  quarter-inch 
glass  tubing  8  in.  long.  Smooth  the  ends.  Push  one  end 
through  a  one-hole  rubber  stopper.  To  the  free  end  fit  an 
ordinary  Welsbach  burner  and  mantle. 

Place  two  tablespoonfuls  of  the  liquid  under  examina- 
tion in  a  Bohemian  flask  and  insert  the  stopper  and  tube. 
Heat  the  flask  gently,  and  if-  alcohol  is  present  in  amounts 
of  over  12  per  cent,  it  will  cause  the  mantle  to  glow  brightly 
when  ignited. 

To  get  the  best  effect,  inclose  the  mantle  in  a  glass  or 
mica  chimney.  Some  brands  of  "bitters,"  "tonics,"  "cures," 
"specifics,"  etc.  contain  enough  alcohol  to  keep  up  the 
incandescence  for  five  or  six  minutes. 

Instead  of  the  Bohemian  flask  one  may  substitute  a  cop- 
per can  fitted  with  a  small  screw  stopper.  Into  the  top  of 


56 


ELEMENTARY  APPLIED  CHEMISTRY 


the  can  solder  a  piece  of  gas  pipe  about  8  in.  long  and  fit 
with  a  burner.    Be  sure  that  all  connections  are  well  made. 


FIG.  14.  Testing  apparatus  to  demonstrate  the  presence  of  alcohol  in 
medicine  and  beverages 

Preparation  of  Alcohol  (C2H5OH).    Dissolve  30  g.  of  cane 
sugar  in  75  cc.  of  water,  add  a  drop  of  HC1,  and  boil  one 


DISTILLATION  EXPERIMENTS  57 

minute.  If  grape  sugar  or  20  cc.  of  molasses  is  used  instead 
of  cane  sugar,  the  boiling  and  acid  may  be  omitted. 

Dissolve  half  a  cake  of  yeast  in  the  same  volume  of  water 
not  above  50°  C.  Cool  the  sugar  solution  to  about  the  same 
temperature  and  mix  with  the  yeast.  Allow  to  remain  in  a 
warm  place  for  two  or  three  days%  and  observe  from  time  to 
time  any  visible  changes. 

Decant  the  liquid  into  a  retort  and  distil  off  about  one 
half.  Wash  the  retort,  pour  in  the  distillate,  and  distil  off 
10  cc.  Test  the  second  distillate  as  follows  : 

Determine  its  odor  and  taste.  In  it  test  the  solubility 
of  a  bit  of  camphor  or  the  oil  from  a  piece  of  orange  or 
lemon  peel.  Burn  a  little  in  an  evaporating  dish.  To 
equal  quantities  of  the  distillate  and  acetic  acid  add  a  few 
drops  of  H2SO4,  taking  care  that  the  contents  of  the  tube 
do  not  spatter  in  your  face.  Heat  gently.  Notice  the 
ethereal,  fruitlike  odor  of  ethyl  acetate,  or  acetic  ether,  a 
substance  much  used  in  the  preparation  of  artificial  flavor- 
ing compounds. 

If  the  experiment  has  been  conducted  properly,  the  fer- 
mented liquid  will  contain  about  4.5  per  cent  of  alcohol 
by  volume. 

Cane  sugar  does  not  ferment.  Treated  properly  with 
acid  the  reaction  probably  takes  place  as  follows: 

C12H22On  +  H20  =  C6H1206  +  C6H1206. 

cane  sugar  glucose  fructose 


The  instructor  or  one  of  the  pupils  should  prepare  a 
flask  of  the  sugar-yeast  mixture.  Fit  a  delivery  tube  so 
that  its  free  end  dips  below  the  surface  of  a  few  cubic  cen- 
timeters of  limewater  contained  in  a  small,  narrow-necked 


58  ELEMENTARY  APPLIED  CHEMISTRY 

bottle.  The  presence  of  CO2,  given  off  during  the  process 
of  fermentation,  is  thus  easily  demonstrated.1 

Determination  of  the  Per  Cent  of  Alcohol  by  Distillation. 
The  chemical  and  physical  characteristics  of  alcohol  are  so 
apparent  that  a  qualitative  analysis  is  seldom  necessary.  It 
is  highly  important,  however,  to  know  how  much  of  this 
substance  enters  into  the  composition  of  various  medicines 
and  articles  intended  for  internal  use.  To  comply  with  the 
Food  and  Drugs  Act,  the  amount  of  alcohol  must  be  plainly 
stated  upon  the  label.  How  does  your  analysis  agree  with 
the  statement  ? 

Introduce  exactly  100  cc.  of  sweet  cider,  beer,  wine,  medi- 
cine, root-beer  extracts,  or  any  of  the  various  "  tonics  "  and 
"  blood  purifiers,"  into  a  retort  and  distil  off  about  one  half, 
being  sure  that  the  free  end  of  the  condenser  dips  deeply 
into  the  receiving  flask.  Make  up  the  distillate  to  exactly 
100  cc.  by  adding  distilled  water.  Determine  the  specific 
gravity  of  the  thoroughly  mixed  distillate,  and  from  this 
determine  the  per  cent  of  alcohol  by  volume  by  means  of 
the  tables  (pp.  66-75). 

Repeat  the  experiment  by  weighing  exactly  100  g.  of 
the  sample  in  a  tared  flask  or  beaker.  Transfer  to  a  retort 
and  distil  as  before. 

Make  the  distillate  up  to  100  g.  with  distilled  water. 
Take  the  specific  gravity.  From  this  determine,  by  means 

1  The  student  will  find  helpful  references  to  alcohol  in  the  following 
publications : 

Popular  Science  Monthly:  "History  of  Alcohol,"  Vol.  LI,  p.  231; 
"Physiology  of  Alcohol,"  Vol.  L,  p.  796;  "Natural  Production  of  Alco- 
hol," Vol.  XIX,  p.  238;  "Discovery  and  Distillation  of  Alcohol,"  Vol. 
XLIII,  p.  85;  "Use  of  Alcohol  in  Medicine,"  Vol.  XXXVIII,  p.  86; 
"Vinous  Superstitions,"  Vol.  XXIV,  p.  234;  "Pigs  as  Wine  Bibbers," 
Vol.  XXIV,  p.  426. 

Farmers'  Bulletin  No.  268,  United  States  Department  of  Agriculture. 


DISTILLATION  EXPERIMENTS 


59 


\ 


i 
/I 


of  the  tables,  the  per  cent  of  alcohol  by  weight.    Discover 
any  mathematical  sequence  in  the  alcohol  tables  (pp.  66~75). 

Suggestions.  Always  carefully  rinse  the  vessel  contain- 
ing the  measured  amount  of  the  sample  into  the  retort, 
using  about  half  its 
volume  of  water. 

Determine  the  tem- 
perature of  the  dis- 
tillate at  which  you 
take  the  specific 
gravity  and  correct 
to  60°  F.  or  15°  C. 
For  all  temperatures 
above  these  stand- 
ards subtract  .00080 
for  each  Centigrade 
degree  or  .00044  for 
each  Fahrenheit  de- 
gree. For  all  temper- 
atures below  these 
standards  the  cor-' 
rection  is  additive. 

If,  for  this  work, 
pupils  are  encour- 
aged to  bring  sam- 
ples from  home,  the 
results  will  often  be 
a  revelation  not  only  to  themselves  but  also  to  their  parents. 

Determination  of  the  Per  Cent  of  Alcohol  by  Difference  in 
Specific  Gravity.  This  method,  suggested  by  Leach,  gives 
approximate  results.  Use  the  preceding  method  whenever 
possible. 


FIG.  15.   Apparatus  for  determining  the 
per  cent  of  alcohol 


60  ELEMENTAKY  APPLIED  CHEMISTKY 

Determine  the  specific  gravity  of  the  original  sample. 
Evaporate  50  cc.  over  a  water  bath  to  one  fourth  its 
.bulk.  Make  up  to  its  original  volume  with  distilled  water. 
Determine  the  specific  gravity  of  this  dealcoholized  por- 
tion. Add  1  to  the  original  specific  gravity  and  subtract  the 
second.  The  difference  corresponds  to  the  alcohol  in  the 
original  sample. 

Consult  the  tables  (pp.  66~75)  as  before  and  read  the 
per  cent  of  alcohol  by  volume. 

Methyl  or  Wood  Alcohol  (CH3OH).  It  is  difficult  to  find  a 
more  dangerous  liquid  used  to  cheapen  food  products  and 
medicinal  preparations  than  methyl  alcohol.  It  is  responsi- 
ble for  many  cases  of  death  and  blindness.  It  apparently 
makes  little  difference  whether  it  is  taken  internally  in 
medicines  and  beverages,  rubbed  on  the  skin  as  a  liniment, 
or  its  vapor  inhaled ;  death,  severe  illness,  or  blindness 
may  result.1 

In  more  instances  than  one  this  poison  has  been  found, 
in  its  deodorized  form,  in  Jamaica  ginger,  lemon  extract, 
peppermint  and  cinnamon,  "  hot  drops,"  liniments,  bitters, 
toilet  waters,  bay  rum,  witch  hazel,  spirits  of  camphor, 
paregoric,  whisky. 

Detection  of  Methyl  Alcohol.  Except  where  a  refractom- 
eter  is  used,  the  presence  of  wood  alcohol  is  proved  indi- 
rectly, usually  by  oxidizing  it  into  formaldehyde. 

Cut  a  piece  of  No.  14  copper  wire  90  cm. -long.  At  a 
point  20  cm.  from  one  end  wind  the  wire  neatly  around  a 
pencil  into  a  close  spiral  until  about  20  cm.  from  the  oppo- 
site end.  Push  the  first  end  through  the  coil  and  twist 
both  together  to  form  a  handle. 

1  For  instances  of  methyl  alcohol  poisoning,  see  Journal  of  the  Ameri- 
can Medical  Association,  October  1-29,  1904. 


DISTILLATION  EXPERIMENTS  61 

Prepare  a  solution  of  1  part  CH3OH  and  6  parts  water. 
Mix,  and  pour  10  cc.  into  a  5-in.  test  tube  whose  inside 
diameter  is  a  little  greater  than  the  diameter  of  the  spiral. 
Stand  the  tube  in  a  bottle  of  cold  water,  to  cool  the  contents 
during  the  oxidizing  process. 

Heat  the  coil  to  a  dull  red  in  the  upper  Bunsen  flame 
and  plunge  immediately  into  the  dilute  alcohol.  Withdraw 
in  a  second  and  dip  into  water.  Repeat  the  operation  from 
three  to  six  times.  This  treatment  will  change  all  or  a 
part  of  the  alcohol  into  formaldehyde. 

CH  OH  -  2  H  =  HCHO. 

o 

CuO  +  2  H  =  ? 

What  reaction  takes  place  when  the  copper  spiral  is 
heated  in  the  upper  Bunsen  flame  ? 

Decant  the  oxidized  liquid  and  divide  into  two  portions. 
Add  one  portion  to  a  little  milk  ancl  apply  the  tests  for 
formaldehyde. 

To  the  other  portion  add  1  drop  of  1  per  cent  resorcin 
solution  and  mix  well.  Pour  this  mixture  carefully  down 
the  side  of  a  wide  test  tube  which  contains  a  half  inch  of 
concentrated  H2SO4.  A  red  ring  (not  brown)  will  form 
between  the  two  liquids.  If  much  formaldehyde  is  present, 
a  precipitate  may  be  seen.  This  is  known  as  Hehner's 
resorcin  test. 

Test  witch  hazel,  lemon  extract,  cheap  vanilla,  etc. 
by  oxidizing  10  cc.  as  indicated.  In  the  case  of  vanilla 
it  is  advisable  to  distil  off  about  10  cc.  and  oxidize  the 
distillate. 

Caution.  One  must  always  be  sure  that  the  original 
sample  does  not  contain  formaldehyde  before  testing  for 
methyl  alcohol,  otherwise  the  results  might  be  misleading. 


62 


ELEMENTARY  APPLIED  CHEMISTRY 


If  there  is  a  question,  add  a  few  drops  of  the   original 
sample  to  5  cc.  of  milk  and  apply  the  Hehner  test. 

All  aldehydes  may  be  removed  by  distilling  50  cc.  of  the 
sample  with  10  g.  of  sodium  bisulfite  and  allowing  the  mix- 
ture to  stand  for  two  hours.  Distil  a  second  time,  and  make 

distinctly  alkaline 
withNaOH.  Oxidize 
this  distillate  and 
test  for  methyl  alco- 
hol (^Report  Massa- 
chusetts State  Board 
of  Health,  1906, 
p.  401). 

Use  of  Alcohol  in 
the    Preparation    of 
Vanilla  Extract.  The 
preparation    of    fla- 
voring extracts  from 
pure  and  high-grade 
materials  is  a  valu- 
able experience  for 
students    of    chem- 
istry.  The  work  can 
be  done  in  the  lab- 
oratory or  at  home. 
Vanilla  extract  is  the  flavoring  extract  prepared  from 
vanilla  beans,  with  or  without  sugar  or  glycerin,  and  con- 
tains in  100  cc.  the  soluble  matters  from  not  less  than 
10  g.  of  the  beans  (£/".  S..  standard). 

Preparation  (United  States  Pharmacopoeia).  Cut  100  g. 
of  vanilla  beans  in  a  meat  chopper,  which  must  be  clean 
and  free  from  foreign  odors.  Weigh  200  g.  of  coarse 


FIG.  16.   Copper  spiral  and  water-cooled  test 

tube  for  the  oxidation  of  methyl  alcohol  into 

formaldehyde 


DISTILLATIOK  EXPERIMENTS  63 

granulated  sugar;  mix  650  cc.  of  alcohol  with  350  cc.  of 
water. 

Macerate  the  vanilla  in  500  cc.  of  this  dilute  alcohol 
for  twelve  hours ;  then  drain  off  the  liquid  and  set  it  aside. 
Transfer  the  vanilla  to  a  mortar  and  beat  it  with  the  sugar. 
Pack  the  mass  into  a  percolator,  the  neck  of  which  has 
been  plugged  with  a  piece  of  absorbent  cotton  from  within, 
and  pour  on  the  reserved  dilute  alcohol.  When  this  has 
disappeared  from  the  surface,  gradually  pour  on  the  men- 
struum and  continue  percolation  until  1000  cc.  have  been 
obtained.  Repercolate  several  times. 

Vanilla  extract  improves  with  age.  If  the  alcoholic  mix- 
ture remains  on  the  beans  for  several  months,  the  flavor  of 
the  extract  will  be  improved. 

To  distinguish  between  True  and  Artificial  Vanilla  Extract. 
Many  of  the  so-called  vanilla  extracts  contain  little  or  no 
vanilla,  but  are  composed  of  a  dilute  alcoholic  solution  of 
vanillin,  or  coumarin,  prepared  from  coal  tar.  Sometimes 
true  coumarin,  the  aromatic  principle  of  the  tonka  or 
"  snuff  "  bean,  is  added  to  make  the  flavor  more  pronounced 
and  lasting.  Such  extracts  are  often  colored  with  caramel 
or  with  coal-tar  dye. 

Some  experience  is  necessary  to  distinguish  between  true 
and  artificial  extracts  by  a  sense  of  smell  or  taste  alone,  but 
there  are  several  chemical  tests  which  will  definitely  settle 
the  matter. 

By  the  Lead  Acetate  Precipitate.  To  40  cc.  of  the  sample 
add  an  equal  volume  of  normal  lead  acetate  solution  pre- 
pared by  dissolving  189.5  g.  of  Pb(C2H3O2)24- 3  H2O  in 
water  and  diluting  to  1  liter. 

The  absence  of  a  precipitate  is  conclusive  evidence  that 
the  extract  is  artificial.  Pure  vanilla  thus  treated  yields  a 


64    ELEMEKTAKY  APPLIED  CHEMISTRY 

heavy  precipitate  which  should  settle  in  a  few  minutes, 
leaving  a  clear,  partially  decolorized  liquid  (Leach). 

By  Examination  of  the  Resins  Present.  Evaporate  the  alco- 
hol from  50  cc.  of  the  extract  over  a  water  bath  and 
make  up  to  the  original  volume  with  water.  If  an  alkali 
(usually  K2CO3)  has  not  been  used  in  the  manufacture  of 
the  extract,  the  resins  will  appear  as  a  flocculent  red  to 
brown  residue.  Acidify  with  acetic  acid,  allow  to  stand  for 
a  few  minutes,  and  collect  the  resins  on  a  filter  paper. 
Wash  the  residue  twice  with  slightly  warmed  water. 

Tear  off  a  portion  of  the  filter  paper  with  the  resins 
attached,  and  place  it  in  a  few  cubic  centimeters  of  dilute 
KOH.  If  the  vanilla  is  pure,  this  resin  will  dissolve,  making 
a  deep  red  solution. 

Dissolve  the  rest  of  the  resin  in  alcohol  and  divide  the 
solution  into  three  parts: 

(a)  Add  a  few  drops  of  ferric  chlorid.    There  will  be  no 
particular  change  if  the  vanilla  is  pure. 

(b)  Add  a  few  drops  of  dilute  HC1.    If  the  vanilla  is 
pure,  there  will  be  no  particular  color  change. 

(c)  Add  a  few  drops  of  lead  subacetate   solution.    If 
the  vanilla  is  pure,  the  precipitate  will  be  so  bulky  as  to 
almost  solidify.   Its  filtrate  will  be  almost  colorless  (Bulletin 
No.  107,  revised). 

Use  of  Alcohol  in  the  Preparation  of  Lemon  Extract. 
Lemon  extract  is  the  flavoring  extract  prepared  from  the  oil 
of  lemon  or  from  lemon  peel,  or  both,  and  contains  not  less 
than  5  per  cent  by  volume  of  lemon  oil  (  U.  !S.  standard). 

An  extract  of  fair  quality,  but  which  does  not  contain  the 
legal  amount  of  lemon  oil,  may  be  prepared  by  grating  the 
yellow  rind  from  six  lemons  and  macerating  in  40  per  cent 
alcohol  for  a  few  days.  It  can  then  be  filtered  and  used. 


DISTILLATION  EXPERIMENTS  65 

A  legal  extract  can  be  prepared  by  dissolving  1  oz.  of 
lemon  oil  in  19  oz.  of  alcohol.  This  extract  can  then  be 
colored,  if  desired,  by  the  addition  of  some  of  the  bright 
yellow  solution  prepared  from  the  lemon  peel. 

Approximate  Test  for  Strength  and  Purity.  To  50  cc.  of 
cold  water  add  2  cc.  of  the  lemon  extract.  The  oil  will  be 
thrown  out  of  solution,  giving  the  top  of  the  water  column  a 
decided  milky  appearance.  The  depth  of  the  milkiness,  in  a 
measure,  enables  one  to  judge  of  the  strength  of  the  extract. 
Absence  of  the  milky  color  is  conclusive  proof  that  the 
extract  is  artificial.  If  it  is  of  a  decided  yellow  color,  test 
for  artificial  color  as  directed  under  Coal-Tar  Dye. 

Per  Cent  of  Lemon  Oil.  Mitchell's  Test.  Place  20  cc.  of 
the  extract  in  a  Babcock  milk  bottle.  Add  1  cc.  dilute  HC1 
(1  to  1)  and  about  28  cc.  of  warm,  water  at  60°  C.  Mix 
and  allow  the  bottle  to  stand  in  warm  water  at  the  same 
temperature  for  five  minutes.  Centrifuge  for  five  minutes. 
Add  warm  water  to  bring  the  oil  into  the  graduated  neck. 
Centrifuge  for  two  minutes  more  and  stand  the  bottle  in 
water  at  60°  C.  up  to  the  top  of  the  oil  column  for  a  few 
minutes,  and  read  the  per  cent  of  oil  by  volume. 

If  more  than  2  per  cent  of  oil  is  present,  add  0.4  per 
cent  to  correct  for  the  oil  retained  in  solution.  If  between 
1  and  2  per  cent,  add  0.3  per  cent  for  correction. 


66 


ELEMENTARY  APPLIED  CHEMISTEY 


TABLE  FOR  DETERMINATION  OF  ALCOHOL  PER- 
CENTAGES ! 

BY  SQUIBB,  DRINKWATER,  AND  GILPIN 


SPECIFIC 
GRAVITY 

AT  f  §0  F. 

ALCOHOL 

SPECIFIC 
GRAVITY 

ATfg°F. 

ALCOHOL 

SPECIFIC 
GRAVITY 

ATfgoF. 

ALCOHOL 

Pel- 
cent 
by  vol- 
ume 

Pel- 
cent 
by 

weight 

Per 

cent 
by  vol- 
ume 

Per 
cent 
by 

weight 

Per 
cent 
by  vol- 
ume 

Per 

cent 

by 

weight 

1.00000 

0.00 

0.00 

0.99775 

1.50 

1.19 

0.99557 

3.00 

2.39 

0.99992 

0.05 

0.04 

.99768 

1.55 

1.23 

.99550 

3.05 

2.43 

.99984 

0.10 

0.08 

.99760 

1.60 

1.27 

.99543 

3.10 

2.47 

.99976 

0.15 

0.12 

.99753 

1.65 

1.31 

.99536 

3.15 

2.51 

.99968 

0.20 

0.16 

.99745 

1.70 

1.35 

.99529 

3.20 

2.55 

.99961 

0.25 

0.20 

.99738 

1.75 

1.39 

.99522 

3.25 

2.59 

.99953 

0.30 

0.24 

.99731 

1.80 

1.43 

.99515 

3.30 

2.64 

.99945 

0.35 

0.28 

.99723 

1.85 

1.47 

.99508 

3.35 

2.68 

.99937 

0.40 

0.32 

.99716 

1.90 

1.51 

.99501 

3.40 

2.72 

.99930 

0.45 

0.36 

.99708 

1.95 

1.55 

.99494 

3.45 

2.76 

.99923 

0.50 

0.40 

.99701 

2.00 

1.59 

.99487 

3.50 

2.80 

.99915 

0.55 

0.44 

.99694 

2.05 

1.63 

.99480 

3.55 

2.84 

.99907 

0.60 

0.48 

.99687 

2.10 

1.67 

.99473 

3.60 

2.88 

.99900 

0.65 

0.52 

.99679 

2.15 

1.71 

.99466 

3.65 

2.92 

.99892 

0.70 

0.56 

.99672 

2.20 

1.75 

.99459 

3.70 

2.96 

.99884 

0.75 

0.60 

.99665 

2.25 

1.79 

.99452 

3.75 

3.00 

.99877 

0.80 

0.64 

.99658 

2.30 

1.83 

.99445 

3.80 

3.04 

.99869 

0.85 

0.67 

.99651 

2.35 

1.87 

.99438 

3.85 

3.08 

.99861 

0.90 

0.71 

.99643 

2.40 

1.91 

.99431 

3.90 

3.12 

.99854 

0.95 

0.75 

.99636 

2.45 

1.95 

.99424 

3.95 

3.16 

.99849 

.00 

0.79 

.99629 

2.50 

1.99 

.99417 

4.00 

3.20 

.99842 

.05 

0.83 

.99622 

2.55 

2.03 

.99410 

4.05 

3.24 

.99834 

.10 

0.87 

.99615 

2.60 

2.07 

.99403 

4.10 

3.28 

.99827 

.15 

0.91 

.99607 

2.65 

2.11 

.99397 

4.15 

3.32 

.99819 

.20 

0.95 

.93600 

2.70 

2.15 

.99390 

4.20 

3.36 

.99812 

.25 

0.99 

.99593 

2.75 

2.19 

.99383 

4.25 

3.40 

.99805 

.30 

1.03 

.99586 

2.80 

2.23 

.99376 

4.30 

3.44 

.99797 

.35 

1.07 

.99579 

2.85 

2.27 

.99369 

4.35 

3.48 

.99790 

.40 

1.11 

.99571 

2.90 

2.31 

.99363 

4.40 

3.52 

.99782 

.45 

1.15 

.99564 

2.95 

2.35 

.99356 

4.45 

3.56 

1  From  Bulletin  No.  107,  United  States  Department  of  Agriculture. 


PERCENTAGE  OF  ALCOHOL 


67 


PERCENTAGE  OF  ALCOHOL  (CONTINUED) 


SPECIFIC 
GRAVITY 

ATgg°F. 

ALCOHOL 

SPECIFIC 
GRAVITY 

AT  f  go  F. 

ALCOHOL 

SPECIFIC 
GRAVITY 

ATfgOF. 

ALCOHOL 

Per 

cent 
by  vol- 
ume 

Pei- 
cent 
by 
weight 

Per 
cent 
by  vol- 
ume 

Per 

cent 

by 
weight 

Per 

cent 
by  vol- 
ume 

Pei- 
cent 

by 

weight 

0.99349 

4.50 

3.60 

0.99117 

6.25 

5.00 

0.98897 

8.00 

6.42 

.99342 

4.55 

3.64 

.99111 

6.30 

5.05 

.98891 

8.05 

6.46 

.99335 

4.60 

3.68 

.99104 

6.35 

5.09 

.98885 

8.10 

6.50 

.99329 

4.65 

3.72 

.99098 

6.40 

5.13 

.98879 

8.15 

6.54 

.99322 

4.70 

3.76 

.99091 

6.45 

5.17 

.98873 

8.20 

6.58 

.99315 

4.75 

3.80 

.99085 

6.50 

5.21 

.98867 

8.25 

6.62 

.99308 

4.80 

3.84 

.99079 

6.55 

5.25 

.98861 

8.30 

6.67 

.99301 

4.85 

3.88 

.99072 

6.60 

5.29 

.98855 

8.35 

6.71 

.99295 

4.90 

3.92 

.99066 

6.65 

5.33 

.98849 

8.40 

6.75 

.99288 

4.95 

3.96 

.99059 

6.70 

5.37 

.98843 

8.45 

6.79 

.99281 

5.00 

4.00 

.99053 

6.75 

5.41 

.98837 

8.50 

6.83 

.99274 

5.05 

4.04 

.99047 

6.80 

5.45 

.98831 

8.55 

6.87 

.992(38 

5.10 

4.08 

.99040 

6.85 

5.49 

.98825 

8.60 

6.91 

.99261 

5.15 

4.12 

.99034 

6.90 

5.53 

.98819 

8.65 

6.95 

.99255 

5.20 

4.16 

.99027 

6.95 

5.57 

.98813 

8.70 

6.99 

.99248 

5.25 

4.20 

.99021 

7.00 

5.61 

.98807 

8.75 

7.03 

.99241 

5.30 

4.24 

.99015 

7.05 

5.65 

.98801 

8.80 

7.07 

.99235 

5.35 

4.28 

.99009 

7.10 

5.69 

.98795 

8.85 

7.11 

.99228 

5.40 

4.32 

.99002 

7.15 

5.73 

.98789 

8.90 

7.15 

.99222 

5.45 

4.36 

.98996 

7.20 

5.77 

.98783 

8.95 

7.19 

.99215 

5.50 

4.40 

.98990 

7.25 

5.81 

.98777 

9.00 

7.23 

.99208 

5.55 

4.44 

.98984 

7.30 

5.86 

.98771 

9.05 

7.27 

.99202 

5.60 

4.48 

.98978 

7.35 

5.90 

.98765 

9.10 

7.31 

.99195 

5.65 

4.52 

.98971 

7.40 

5.94 

.98759 

9.15 

7.35 

.99189 

5.70 

4.56 

.98965 

7.45 

5.98 

.98754 

9.20 

7.39 

.99182 

5.75 

4.60 

.98959 

7.50 

6.02 

.98748 

9.25 

7.43 

.99175 

5.80 

4.64 

.98953 

7.55 

6.06 

.98742 

9.30 

7.48 

.99169 

5.85 

4.68 

.98947 

7.60 

6.10 

.98736 

9.35 

7.52 

.99162 

5.90 

4.72 

.98940 

7.65 

6.14 

.98730 

9.40 

7.56 

.99156 

5.95 

4.76 

.98934 

7.70 

6.18 

.98724 

9.45 

7.60 

.99149 

6.00 

4.80 

.98928 

7.75 

6.22 

.98719 

9.50 

7.64 

.99143 

6.05 

4.84 

.98922 

7.80 

6.26 

.98713 

9.55 

7.68 

.99136 

6.10 

4.88 

.98916 

7.85 

6.30 

.98707 

9.60 

7.72 

.99130 

6.15 

4.92 

.98909 

7.90 

6.34 

.98701 

9.65 

7.76 

.99123 

6.20 

4.96 

.98903 

7.95 

6.38 

.98695 

9.70 

7.80 

68  ELEMENTAKY  APPLIED  CHEMISTRY 

PERCENTAGE  OF  ALCOHOL  (CONTINUED) 


SPECIFIC 
GRAVITY 

AT  ggo  F. 

ALCOHOL 

SPECIFIC 
GRAVITY 
AT  gg°  F. 

AXCOHOL 

SPECIFIC 
GRAVITY 

AT  g§0  F. 

ALCOHOL 

Per 

cent 
by  vol- 
ume 

Pel- 
cent 
by 
weight 

Per 
cent 
by  vol- 
ume 

Pei- 
cent 
by 

weight 

Per 
cent 
by  vol- 
ume 

Per 

cent 

by 
weight 

0.98689 

9.75 

7.84 

0.98491 

11.50 

9.27 

0.98299 

13.25 

10.69 

.98683 

9.80 

7.88 

.98485 

11.55 

9.31 

.98294 

13.30 

10.74 

.98678 

9.85 

7.92 

.98479 

11.60 

9.35 

.98289 

13.35 

10.78 

.98672 

9.90 

7.96 

.98474 

11.65 

9.39 

.98283 

13.40 

10.82 

.98666 

9.95 

8.00 

.98468 

11.70 

9.43 

.98278 

13.45 

10.86 

.98660 

10.00 

8.04 

.98463 

11.75 

9.47 

.98273 

13.50 

10.90 

.98654 

10.05 

8.08 

.98457 

11.80 

9.51 

.98267 

13.55 

10.94 

.98649 

10.10 

8.12 

.98452 

11.85 

9.55 

.98262 

13.60 

10.98 

.98643 

10.15 

8.16 

.98446 

11.90 

9.59 

.98256 

13.65 

11.02 

.98637 

10.20 

8.20 

.98441 

11.95 

9.63 

.98251 

13.70 

11.06 

.98632 

10.25 

8.24 

.98435 

12.00 

9.67 

.98246 

13.75 

11.11 

.98626 

10.30 

8.29 

.98430 

12.05 

9.71 

.98240 

13.80 

11.15 

.98620 

10.35 

8.33 

.98424 

12.10 

9.75 

.98235 

13.85 

11.19 

.98614 

10.40 

8.37 

.98419 

12.15 

9.79 

.98230 

13.90 

11.23 

.98609 

10.45 

8.41 

.98413 

12.20 

9.83 

.98224 

13.95 

11.27 

.98603 

10.50 

8.45 

.98408 

12.25 

9.87 

.98219 

14.00 

11.31 

.98597 

10.55 

8.49 

.98402 

12.30 

9.92 

.98214 

14.05 

11.35 

.98592 

10.60 

8.53 

.98397 

12.35 

9.96 

.98209 

14.10 

11.39 

.98586 

10.65 

8.57 

.98391 

12.40" 

10.00 

.98203 

14.15 

11.43 

.98580 

10.70 

8.61 

.98386 

12.45 

10.04 

.98198 

14.20 

11.47 

.98575 

10.75 

8.65 

.98381 

12.50 

10.08 

.98193 

14.25 

11.52 

.98569 

10.80 

8.70 

.98375 

12.55 

10.12 

.98188 

14.30 

11.56 

.98563 

10.85 

8.74 

.98370 

12.60 

10.16 

.98182 

14.35 

11.60 

.98557 

10.90 

8.78 

.98364 

12.65 

10.20 

.98177 

14.40 

11.64 

.98552 

10.95 

8.82 

.98359 

12.70 

10.24 

.98172 

14.45 

11.68 

.98546 

11.00 

8.86 

.98353 

12.75 

10.28 

.98167 

14.50 

11.72 

.98540 

11.05 

8.90 

.98348 

12.80 

10.33 

.98161 

14.55 

11.76 

.98535 

11.10 

8.94 

.98342 

12.85 

10.37 

.98156 

14.60 

11.80 

.98529 

11.15 

8.98 

.98337 

12.90 

10.41 

.98151 

14.65 

11.84 

.98524 

11.20 

9.02 

.98331 

12.95 

10.45 

.98146 

14.70 

11.88 

.98518 

11.25 

9.07 

.98326 

13.00 

10.49 

.98140 

14.75 

11.93 

.98513 

11.30 

9.11 

.98321 

13.05 

10.53 

.98135 

14.80 

11.97 

.98507 

11.35 

9.15 

.98315 

13.10 

10.57 

.98130 

14.85 

12.01 

.98502 

11.40 

9.19 

.98310 

13.15 

10.61 

.98125 

14.90 

12.05 

.98496 

11.45 

9.23 

.98305 

13.20 

10.65 

.98119 

14.95 

12.09 

PERCENTAGE  OF  ALCOHOL 


69 


PERCENTAGE  OF  ALCOHOL  (CONTINUED) 


SPECIFIC 
GRAVITY 

AT|§°F. 

ALCOHOL 

SPECIFIC 
GRAVITY 

ATggOF. 

ALCOHOL 

SPECIFIC 
ORAVITY 

AT|g°F. 

ALCOHOL 

Pei- 
cent 
by  vol- 
ume 

Pei- 
cent 
by 
weight 

Per 
cent 
by  vol- 
ume 

Per 
cent 
by 

weight 

Per 
cent 
by  vol- 
ume 

Per 

cent 
by 
weight 

0.98114 

15.00 

12.13 

0.97935 

16.75 

13.57 

0.97758 

18.50 

15.02 

.98108 

15.05 

12.17 

.97929 

16.80 

13.62 

.97753 

18.55 

15.06 

.98104 

15.10 

12.21 

.97924 

16.85 

13.66 

.97748 

18.60 

15.10 

.98099 

15.15 

12.25 

.97919 

16.90 

13.70 

.97743 

18.65 

15.14 

.98093 

15.20 

12.29 

.97914 

16.95 

13.74 

.97738 

IB.  70 

15.18 

.98088 

15.25 

12.33 

.97909 

17.00 

13.78 

.97733 

18.75 

15.22 

.98083 

15.30 

12.38 

.97904 

17.05 

13.82 

.97728 

18.80 

15.27 

.98078 

15.35 

12.42 

.97899 

17.10 

13.86 

.97723 

18.85 

15.31 

.98073 

15.40 

12.46 

.97894 

17.15 

13.90 

.97718 

18.90 

15.38 

.98008 

15.45 

12.50 

.97889 

17.20 

13.94 

.97713 

18.95 

15.39 

..98063 

15.50 

12.54 

.97884 

17.25 

13.98 

.97708 

19.00 

15.43 

.98057 

15.55 

12.58 

.97879 

17.30 

14.03 

.97703 

19.05 

15.47 

.98052 

15.60 

12.62 

..97874 

17.35 

14.07 

.97698 

19.10 

15.51 

.98047 

15.65 

12.66 

.97869 

17.40 

14.11 

.97693 

19.15 

15.55 

.98042 

15.70 

12.70 

.97864 

17.45 

14.15 

.97688 

19.20 

15.59 

.98037 

15.75 

12.75 

.97859 

17.50 

14.19 

.97683 

19.25 

15.63 

.98032 

15.80 

12.79 

.97853 

17".  55 

14.23 

.97678 

19.30 

15.68 

.98026 

15.85 

12.83 

.97848 

17.60 

14.27 

.97673 

19.35 

15.72 

.98021 

15.90 

12.87 

.97843 

17.65 

14.31 

.97668 

19.40 

15.76 

.98016 

15.95 

12.91 

.97838 

17.70 

14.35 

.97663 

19.45 

15.80 

.98011 

16.00 

12.95 

.97.833 

17.75 

14.40 

.97658 

19.50 

15.84 

.98005 

16.05 

12.99 

.97828 

17.80 

14.44 

.97653 

19.55 

15.88 

.98001 

16.10 

13.03 

.97823 

17.85 

14.48 

.97648 

19.60 

15.93 

.9799(5 

16.15 

13.08 

.97818 

17.90 

14.52 

.97643 

19.65 

15.97 

.97991 

16.20 

13.12 

.97813 

17.95 

14.56 

.97638 

19.70 

16.01 

.97986 

16.25 

13.16 

.97808 

18.00 

14.60 

.97633 

19.75 

16.05 

.97980 

16.30 

13.20 

.97803 

18.05 

14.64 

.97628 

19.80 

16.09 

.97975 

16.35 

13.24 

.97798 

18.10 

14.68 

.97623 

19.85 

16.14 

.97970 

16.40 

13.29 

.97793 

18.15 

14.73 

.97618 

19.90 

16.18 

.97965 

16.45 

13.33 

.97788 

18.20 

14.77 

.97613 

19.95 

16.22 

.97960 

16.50 

13.37 

.97783 

18.25 

14.81 

.97608 

20.00 

16.26 

.97955 

16.55 

13.41 

.97778 

18.30 

14.85 

.97603 

20.05 

16.30 

.97950 

16.60 

13.45 

.97773 

18.35 

14.89 

.97598 

20.10 

16.34 

.97945 

16.65 

13.49 

.97768 

18.40 

14.94 

.97593 

20.15 

16.38 

.97940 

16.70 

13.53 

.97763 

18.45 

14.98 

.97588 

20.20 

16.42 

70 


ELEMENTARY  APPLIED  CHEMISTRY 


PERCENTAGE  OF  ALCOHOL  (CONTINUED) 


SPECIFIC 
GRAVITY 

AT  igop. 

ALCOHOL 

SPECIFIC 
GRAVITY 

AT  f  §0  F. 

ALCOHOL 

SPECIFIC 
GRAVITY 

ATfgOF. 

ALCOHOL 

Per 

cent 
by  vol- 
ume 

Per 

cent 
by 
weigh  i 

Per 

cent 
by  vol- 
ume 

Per 

cent 
by 
weight 

Per 
cent 
by  vol- 
ume 

Per 

cent 
by 
weight 

0.97583 

20.25 

16.46 

0.97406 

22.00 

17.92 

0.97227 

23.75 

19.38 

.97578 

20.30 

16.51 

.97401 

22.05 

17.96 

.97222 

23.80 

19.42 

.97573 

20.35 

16.58 

.97396 

22.10 

18.00 

.97216 

23.85 

19.46 

.97568 

20.40 

16.59 

.97391 

22.15 

18.05 

.97211 

23.90 

19.51 

.97563 

20.45 

16.63 

.97386 

22.20 

18.09 

.97206 

23.95 

19.55 

.97558 

20.50 

16.67 

.97381 

22.25 

18.13 

.97201 

24.00 

19.59 

.97552 

20.55 

16.71 

.97375 

22.30 

18.17 

.97196 

24.05 

19.63 

.97547 

20.60 

16.75 

.97370 

22.35 

18.21 

.97191 

24.10 

19.67 

.97542 

20.65 

16.80 

.97365 

22.40 

18.26 

.97185 

24.15 

19.72 

.97537 

20.70 

16.84 

.97360 

22.45 

18.30 

.97180 

24.20 

19.76 

.97532 

20.75 

16.88 

.97355 

22.50 

18.34 

.97175 

24.25 

19.80 

.97527 

20.80 

16.92 

.97350 

22.55 

18.38 

.97170 

24.30 

19.84 

.97522 

20.85 

16.96 

.97345 

22.60 

18.42 

.97165 

24.35 

19.88 

.97517 

20.90 

17.01 

.97340 

22.65 

18.47 

.97159 

24.40 

19.93 

.97512 

20.95 

17.05 

.97335 

22.70 

18.51 

.97154 

24.45 

19.97 

.97507 

21.00 

17.09 

.97330 

22.75 

18.55 

.97149 

24.50 

20.01 

.97502 

21.05 

17.13 

.97324 

22.80 

18.59 

.97144 

24.55 

20.05 

.97497 

21.10 

17.17 

.97319 

22.85 

18.63 

.97139 

24.60 

20.09 

.97492 

21.15 

17.22 

.97314 

22.90 

18.68 

.97133 

24.65 

20.14 

.97487 

21.20 

17.26 

.97309 

22.95 

18.72 

'  .97128 

24.70 

20.18 

.97482 

21.25 

17.30 

.97304 

23.00 

18.76 

.97123 

24.75 

20.22 

.97477 

21.30 

17.34 

.97299 

23.05 

18.80 

.97118 

24.80 

20.26 

.97472 

21.35 

17.38 

.97294 

23.10 

18.84 

.97113 

24.85 

20.30 

.97467 

21.40 

17.43 

.97289 

23.15 

18.88 

.97107 

24.90 

20.35 

.97462 

21.45 

17.47 

.97283 

23.20 

18.92 

.97102 

24.95 

20.39 

.97457 

21.50 

17.51 

.97278 

23.25 

18.96 

.97097 

25.00 

20.43 

.97451 

21.55 

17.55 

.97273 

23.30 

19.01 

.97092 

25.05 

20.47 

.97446 

21.60 

17.59 

.97268 

23.35 

19.05 

.97086 

25.10 

20.51 

.97441 

21.65 

17.63 

.97263 

23.40 

19.09 

.97081 

25.15 

20.56 

.97436 

21.70 

17.67 

.97258 

23.45 

19.13 

.97076 

25.20 

20.60 

.97431 

21.75 

17.71 

.97253 

23.50 

19.17 

.97071 

25.25 

20.64 

.97426 

21.80 

17.76 

.97247 

23.55 

19.21 

.97065 

25.30 

20.68 

.97421 

21.85 

17.80 

.97242 

23.60 

19.25 

.97060 

25.35 

20.72 

.97416 

21.90 

17.84 

.97237 

23.65 

19.30 

.97055 

25.40 

20.77 

.97411 

21.95 

17.88 

.97232 

23.70 

19.34 

.97049 

25.45 

20.81 

PEKCENTAGE  OF  ALCOHOL 


71 


PERCENTAGE  OF  ALCOHOL  (CONTINUED) 


SPECIFIC 
GRAVITY 

AT§8°F. 

ALCOHOL 

SPECIFIC 
GRAVITY 
ATgg°F. 

ALCOHOL 

SPECIFIC 
GRAVITY 

AT|S°F. 

ALCOHOL 

Per 
cent 
by  vol- 
ume 

Per 

cent 

by 

weight 

Per 

cent 
by  vol- 
ume 

Per 

cent 
by 

weight 

Per 

cent 
by  vol- 
ume 

Per 
cent 

by 

weight 

0.97044 

25.50 

20.85 

0.96855 

27.25 

22.33 

0.96658 

29.00 

23.81 

.97039 

25.55 

20.89 

.96850 

27.30 

22.37 

.96652 

29.05 

23.85 

.97033 

25.60 

20.93 

.96844 

27.35 

22.41 

.96646 

29.10 

23.89 

.97028 

25.65 

20.98 

.96839 

27.40 

22.45 

.96640 

29.15 

23.94 

.97023 

25.70 

21.02 

.96833 

27.45 

22.50 

.96635 

29.20 

23.98 

.97018 

25.75 

21.06 

.96828 

27.50 

22.54 

.96629 

29.25 

24.02 

.97012 

25.80 

21.10 

.96822 

27.55 

22.58 

.96623 

29.30 

24.06 

.97007 

25.85 

21.14 

.96816 

27.60 

22.62 

.96617 

29.35 

24.10 

.97001 

25.90 

21.19 

.96811 

27.65 

22.67 

.96611 

29.40 

24.15 

.96996 

25.95 

21.23 

.96805 

27.70 

22.71 

.96605 

29.45 

24.19 

.96991 

26.00 

21.27 

.96800 

27.75 

22.75 

.96600 

29.50 

24.23 

.96986 

26.05 

21.31 

.96794 

27.80 

22.79 

.96594 

29.55 

24.27 

.96980 

26.10 

21.35 

.96789 

27.85 

22.83 

.96587 

29.60 

24.32 

.96975 

26.15 

21.40 

.96783 

27.90 

22.88 

.96582 

29.65 

24.36 

.96969 

20.20 

21.44 

.96778 

27.95 

22.92 

.96576 

29.70 

24.40 

.96964 

26.25 

21.48 

.96772 

28.00 

22.96 

.96570 

29.75 

24.45 

.90959 

26.30 

21.52 

.96766 

28.05 

23.00 

.96564 

29.80 

24.49 

.96953 

26.35 

21.56 

.96761 

28.10 

23.04 

.96559 

29.85 

24.53 

.96949 

26.40 

21.61 

.96755 

28.15 

23.09 

.96553 

29.90 

24.57 

.901)42 

26.45 

21.65 

.96749 

28.20 

23.13 

.96547 

29.95 

24.62 

.96937 

26.50 

21.69 

.96744 

28.25 

23.17 

.96541 

30.00 

24.66 

.96932 

26.55 

21.73 

.96738 

28.30 

23.21 

.96535 

30.05 

24.70 

.96926 

26.60 

21.77 

.96732 

28.35 

23.25 

.96529 

30.10 

24.74 

.96921 

26.65 

21.82 

.96726 

28.40 

23.30 

.96523 

30.15 

24.79 

.96915 

26.70 

21.86 

.96721 

28.45 

23.34 

.96517 

30.20 

24.83 

.96910 

26.75 

21.90 

.96715 

28.50 

23.38 

.96511 

30.25 

24.87 

.96906 

26.80 

21.94 

.96709 

28.55 

23.42 

.96505 

30.30 

24.91 

.96899 

26.85 

21.98 

.96704 

28.60 

23.47 

.96499 

30.35 

24.95 

.96894 

26.90 

22.03 

.96698 

28.65 

23.51 

.96493 

30.40 

25.00 

.96888 

26.95 

22.07 

.96692 

28.70 

23.55 

.96487 

30.45 

25.04 

.96883 

27.00 

22.11 

.96687 

28.75 

23.60 

.96481 

30.50 

25.08 

.96877 

•27.05 

22.15 

.96681 

28.80 

23.64 

.96475 

30.55 

25.12 

.96872 

27.10 

22.20 

.96675 

28.85 

23.68 

.96469 

30.60 

25.17 

,96866 

27.15 

22.24 

.96669 

28.90 

23.72 

.96463 

30.65 

25.21 

.96861 

27.20 

22.28 

.96664 

28.95 

23.77 

.96457 

30.70 

25.25 

72 


ELEMENTARY  APPLIED  CHEMISTRY 


PERCENTAGE  OF  ALCOHOL  (CONTINUED) 


SPECIFIC 
GRAVITY 

AT  |g°  F. 

ALCOHOL 

SPECIFIC 
GRAVITY 

AT  |§0  F. 

ALCOHOL 

SPECIFIC 
GRAVITY 

ATg§°F. 

ALCOHOL 

Per 

cent 
by.  vol- 
ume 

Per 
cent 
by 

weigh 

Per 

cent 
by  vol- 
ume 

Pei- 
cent 

i>y 

weight 

Per 

cent 
by  vol- 
ume 

Per 
cent 
bj 

weight 

0.96451 

30.75 

25.30 

0.96235 

32.50 

26.80 

0.96010 

34.25 

28.31 

.90445 

30.80 

25.34 

.96229 

32.55 

26.84 

.96003 

34.30 

28.35 

.96439 

30.85 

25.38 

.96222 

32.60 

26.89 

.95996 

34.35 

28.39 

.96433 

30.90 

25.42 

.96216 

32.65 

26.93 

.96990 

34.40 

28.43 

.96427 

30.95 

25.47 

.96210 

32.70 

26.97 

.95983 

34.45 

28.48 

.96421 

31.00 

25.51 

.96204 

32.75 

27.02 

.95977 

34.50 

28.52 

.96415 

31.05 

25.55 

.96197 

32.80 

27.06 

.95970 

34.55 

28.56 

.96409 

31.10 

25.60 

.96191 

32.85 

27.10 

.95963 

34.60 

28.61 

.96403 

31.15 

25.64 

.96185 

32.90 

27.14 

.95957 

34.65 

28.05 

.96396 

31.20 

25.68 

.96178 

32.95 

27.19 

.95950 

34.70 

28.70 

.96390 

31.25 

25.73 

.96172 

33.00 

27.23 

.95943 

34.75 

28.74 

.96384 

31.30 

25.77 

.96166 

33.05 

27.27 

.95937 

34.80 

28.78 

.96378 

31.35 

25.81 

.96159 

33.10 

27.32 

.95930 

34.85 

28.83 

.96372 

31.40 

25.85 

.96153 

33.15 

27.36 

.95923 

34.90 

28.87 

.96366 

31.45 

25.90 

.96146 

33.20 

27.40 

.95917 

34.95 

28.92 

.96360 

31.50 

25.94 

.96140 

33.25 

27.45 

.95910 

'35.00 

28.96 

.96353 

31.55 

25.98' 

.96133 

33.30 

27.49 

.95903 

35.05 

29.00 

.96347 

31.60 

26.03 

.96127 

33.35 

27.53 

.95896 

35.10 

29.05 

.96341 

31.65 

26.07 

-.96120 

33.40 

27.57 

.95889 

35.15 

29.09 

.96335 

31.70 

26.11 

.96114 

33.45 

27.62 

.95883 

35.20 

29.13 

.96329 

31.75 

26.16 

.96108 

33.50 

27.66 

.95870 

35.25 

29.18 

.96323 

31.80 

26.20 

.96101 

33.55 

27.70 

.95869 

35.30 

29.22 

.96316 

31.85 

26.24 

.96095 

33.60 

27.75 

.958® 

35.35 

29.26 

.96310 

31.90 

26.28 

.96088 

33.65 

27.79 

.95855 

35.40 

29.30 

.96304 

31.95 

26.33 

.96082 

33.70 

27.83 

.95848 

35.45 

29.35 

.96298 

32.00 

26.37 

.96075 

33.75 

27.88 

.95842 

35.50 

29.30 

.96292 

32.05 

26.41 

.96069 

33.80 

27.92 

.95835 

35.55 

29.43 

.96285 

32.10 

26.46 

.96062 

33.85 

27.96 

.95828 

35.60 

29.48 

.96279 

32.15 

26.50 

.96056 

33.90 

28.00 

.95821 

35.65 

29.52 

.96273 

32.20 

26.54 

.96049 

33.95 

28.05 

.95814 

35.70 

29.57 

.96267 

32.25 

26.59 

.96043 

34.00 

28.09 

.95807 

35.75 

29.61 

.96260 

32.30 

26.63 

.96036 

34.05 

28.13 

.95800 

35.80 

29.65 

.96254 

32.35 

26.67 

.96030 

34.10 

28.18 

.95794 

35.85 

29.70 

.96248 

32.40 

26.71 

.96023 

34.15 

28.22 

.95787 

35.90 

29.74 

.96241 

32.45 

26.76 

.96016 

34.20 

28.26 

.95780 

35.95 

29.79 

PERCENTAGE  OF  ALCOHOL 


73 


PERCENTAGE  OF  ALCOHOL  (CONTINUED) 


SPECIFIC 
GRAVITY 

AT  |g°  F. 

ALCOHOL 

SPECIFIC 
GRAVITY 

AT  |8°  F. 

ALCOHOL 

SPECIFIC 
GRAVITY 

AT§8°F. 

ALCOHOL 

Per 

cent 
by  vol- 
ume 

Per 

cent 

by 

weight 

Per 
cent 
by  vol- 
ume 

Per 

cent 
by 

weight 

Per 
cent 
by  vol- 
ume 

Per 
cent 
by 
weight 

0.95773 

36.00 

29.83 

0.95523 

37.75 

31.36 

0.95262 

39.50 

32.90 

.95766 

36.05 

29.87 

.95516 

37.80 

31.40 

.95254 

39.55 

32.95 

.95759 

36.10 

29.92 

.95509 

37.85 

31.45 

.95246 

39.60 

32.99 

.95752 

36.15 

29.96 

.95502 

37.90 

31.49 

.95239 

39.65 

33.04 

.95745 

36.20 

30.00 

.95494 

37.95 

31.54 

.95231 

39.70 

33.08 

.95738 

36.25 

30.05 

.95487 

38.00 

31.58 

.95223 

39.75 

33.13 

.95731 

36.30 

30.09 

.95480 

38.05 

31.63 

.95216 

39.80 

33.17 

.95724 

36.35 

30.13 

.95472 

38.10 

31.67 

.95208 

39.85 

33.22 

.95717 

36.40 

30.17 

.95465 

38.15 

31.72 

.95200 

39.90 

33.27 

.95710 

36.45 

30.22 

.95457 

38.20 

31.76 

.95193 

39.95 

33.31 

.95703 

36.50 

30.26 

.95450 

38.25 

31.81 

.95185 

40.00 

33.35 

.95695 

36.55 

30.30 

.95442 

38.30 

31.85 

.95177 

40.05 

33.39 

.95688 

36.60 

30.35 

.95435 

38.35 

31.90 

.95169 

40.10 

33.44 

.95681 

36.65 

30.39 

.95427 

38.40 

31.94 

.95161 

40.15 

33.48 

.95674 

36.70 

30.44 

.95420 

38.45 

31.99 

.95154 

40.20 

33.53 

.95667 

36.75 

30.48 

.95413 

38.50 

32.03 

.95146 

40.25 

33.57 

.95660 

36.80 

30.52 

.95405 

38.55 

32.07 

.95138 

40.30 

33.61 

.95653 

36.85 

30.57 

.95398 

38.60 

32.12 

.95130 

40.35 

33.66 

.95646 

36.90 

30.61 

.95390 

38.65 

32.16 

.95122 

40.40 

33.70 

.95639 

36.95 

30.66 

.95383 

38.70 

32.20 

.95114 

40.45 

33.75 

.95632 

37.00 

30.70 

.95375 

38.75 

32.25 

.95107 

40.50 

33.79 

.95625 

37.05 

30.74 

.95368 

38.80 

32.29 

.95099 

40.55 

33.84 

.95618 

37.10 

30.79 

.95360 

38.85 

32.33 

.95091 

40.60 

33.88 

.95610 

37.15 

30.83 

.95353 

38.90 

32.37 

.95083 

40.65 

33.93 

.95603 

37.20 

30.88 

.95345 

38.95 

32.42 

.95075 

40.70 

33.97 

.95508 

37.25 

30.92 

.95338 

39.00 

32.46 

.95067 

40.75 

34.02 

.95589 

37.30 

30.96 

.95330 

39.05 

32.50 

.95059 

40.80 

34.06 

.95581 

37.35 

31.01 

.95323 

39.10 

32.55 

.95052 

40.85 

34.11 

-.95574 

37.40 

31.05 

.95315 

39.15 

32.59 

.95044 

40.90 

34.15 

.95567 

37.45 

31.10 

.95307 

39.20 

32.64 

.95036 

40.95 

34.20 

.95560 

37.50 

31.14 

.95300 

39.25 

32.68 

.95028 

41.00 

34.24 

.95552 

37.55 

31.18 

.95292 

39.30 

32.72 

.95020 

41.05 

34.28 

.95545 

37.60 

31.23 

.95284 

39.35 

32.77 

.95012 

41.10 

34.33 

.95538 

37.65 

31.27 

.95277 

39.40 

32.81 

.95004 

41.15 

34.37 

.95531 

37.70 

31.32 

.95269 

39.45 

32.86 

.94996 

41.20 

34.42 

74 


ELEMENTARY  APPLIED  CHEMISTRY 


PERCENTAGE  OF  ALCOHOL  (CONTINUED) 


SPECIFIC 
GKAVITY 

AT|8°F. 

ALCOHOL 

SPECIFIC 
GRAVITY 

AT|8°F. 

ALCOHOL 

SPECIFIC 
GKAVITY 

AT|§°F. 

ALCOHOL 

Per 
cent 
by  vol- 
ume 

Per 
cent 
by 
weight 

Per 
cent 
by  vol- 
ume 

Pei- 
cent 

by 

weight 

Pel- 
cent 
by  vol- 
ume 

Per 
cent 
by 
weight 

0.94988 

41.25 

34.46 

0.94704 

43.00 

36.03 

0.94407 

44.75 

37.62 

.94980 

41.30 

34.50 

.94696 

43.05 

36.08 

.94398 

44.80 

37.66 

.94972 

41.35 

34.55 

.94687 

43.10 

36.12 

.94390 

44.85 

37.71 

.94964 

41.40 

34.59 

.94679 

43.15 

36.17 

.94381 

44.90 

37.76 

.94956 

41.45 

34.64 

.94670 

43.20 

36.21 

.94373 

44.95 

37.80 

.94948 

41.50 

34.68 

.94662 

43.25 

36.23 

.94364 

45.00 

37.84 

.94940 

41.55 

34.73 

.94654 

43.30 

36.30 

.94355 

45.05 

37.81) 

.94932 

41.60 

34.77 

.94645 

43.35 

36.35 

.94346 

45.10 

37.93 

.94924 

41.65 

34.82 

.94637 

43.40 

36.39 

.94338 

45.15 

37.98 

.94916 

41.70 

34.86 

.94628 

43.45 

36.44 

.94329 

45.20 

38.02 

.94908 

41.75 

34.91 

.94620 

43.50 

36.48 

.94320 

45.25 

38.07 

.94900 

41.80 

34.95 

.94612 

43.55 

36.53 

.94311 

45.30 

38.12 

.94892 

41.85 

35.00 

.94603 

43.60 

36.57 

.94302 

45.35 

38.16 

.94884 

41.90 

35.04 

.94595 

43.65 

36.62 

.94294 

45.40 

38.21 

.94876 

41.95 

35.09 

.94586 

43.70 

36.66 

.94285 

45.45 

38.25 

.94868 

42.00 

35.13 

.94578 

43.75 

36.71 

.94276 

45.50 

38.30 

.94860 

42.05 

35.18 

.94570 

43.80 

36.75 

.94267 

45.55 

38.35 

.94852 

42.10 

35.22 

.94561 

43.85 

36.80 

.94258 

45.60 

38.39 

.94843 

42.15 

35.27 

.94553 

43.90 

36.84 

.94250 

45.65 

38.44 

.94835 

42.20 

35.31 

.94544 

43.95 

36.89 

.94241 

45.70 

38.48 

.94827 

42.25 

35.36 

.94536 

44.00 

36.93 

.94232 

45.75 

38.53 

.94810 

42.30 

35.40 

.94527 

44.05 

36.98 

.94223 

45.80 

^38.57 

.94811 

42.35 

35.45 

.94519 

44.10 

37.02 

.94214 

45.85 

38.02 

.94802 

42.40 

35.49 

.94510 

44.15 

37.07 

.94206 

45.90 

38.66 

.94794 

42.45 

35.54 

.94502 

44.20 

37.11 

.94197 

45.95 

38.71 

.94786 

42.50 

35.58 

.94493 

44.25 

37.16 

.94188 

46.00' 

38.75 

.94778 

42.55 

35.63 

.94484 

44.30 

37.21 

.94179 

46.05 

38.80 

.94770 

42.60 

35.67 

.94476 

44.35 

37.25 

.94170 

46.10 

38.84 

.94761 

42.65 

35.72 

.94467 

44.40 

37.30 

.94161 

46.15 

38.89 

.94753 

42.70 

35.76 

.94459 

44.45 

37.34 

.94152 

46.20 

38.93 

.94745 

42.75 

35.81 

.94450 

44.50 

37.39 

.94143 

46.25 

38.98 

.94737 

42.80 

35.85 

.94441 

44.55 

37.44 

.94134 

46.30 

39.03 

.94729 

42.85 

35.90 

.94433 

44.60 

37.48 

.94125 

46.35 

39.07 

.94720 

42.90 

35.94 

.94424 

44.65 

37.53 

.94116 

46.40 

39.12 

.94712 

42.95 

35.99 

.94416 

44.70 

37.57 

.94107 

46.45 

30.16 

PERCENTAGE  OF  ALCOHOL 


75 


PERCENTAGE  OF  ALCOHOL  (CONCLUDED) 


SPECIFIC 
GRAVITY 
AT  f  go  F. 

ALCOHOL 

SPECIFIC 
GRAVITY 

AT  |§°  F. 

ALCOHOL 

SPECIFIC 
GRAVITY 

AT  f  go  F. 

ALCOHOL 

Per 
cent 
by  vol- 
ume 

Per 
cent 
by 
weight 

Per 
cent 
by  vol- 
ume 

Per 
cent 
by 
weight 

Per 
cent 
by  vol- 
ume 

Per 

cent 
by 

weight 

0.04098 

46.50 

39.21 

0.93870 

47.75 

40.37 

0.93636 

49.00 

41.52 

.1)4089 

46.55 

39.26 

.93861 

47.80 

40.41 

.93626 

49.05 

41.57 

.94080 

46.60 

39.30 

.93852 

47.85 

40.46 

.93617 

49.10 

41.61 

.94071 

46.65 

39.35 

.93842 

47.90 

40.51 

.93607 

49.15 

41.66 

.94062 

46.70 

39.39 

.93833 

47.95 

40.55 

.93598 

49.20 

41.71 

.94053 

46.75 

39.44 

.93824 

48.00 

40.60 

.93588 

49.25 

41.76 

.94044 

46.80 

39.49 

.93815 

48.05 

40.65 

.93578 

49.30 

41.80 

.94035 

46.85 

39.53 

.93805 

48.10 

40.69 

.93569 

49.35 

41.85 

.94020 

46.90 

39.58 

.93796 

48.15 

40.74 

.93559 

49.40 

41.90 

.94017 

46.95 

39.62 

.93786 

48.20 

40.78 

.93550 

49.45 

41.94 

.94008 

47.00 

39.67 

.93777 

48.25 

40.83 

.93540 

49.50 

41.99 

.9391)9 

47.05 

39.72 

.93768 

48.30 

40.88 

.93530 

49.55 

42.04 

.93990 

47.10 

39.76 

.93758 

48.35 

40.92 

.93521 

49.60 

42.08 

.93980 

47.15 

39.81 

.93749 

48.40 

40.97 

.93511 

49.65 

42.13 

.93971 

47.20 

39.85 

.93739 

48.45 

41.01 

.93502 

49.70 

42.18 

.93962 

47.25 

39.90 

.93730 

48.50 

41.06 

.93492 

49.75 

42.23 

.93953 

47.30 

39.95 

.93721 

48.55 

41.11 

.93482 

49.80 

42.27 

.93944 

47.35 

39.99 

.93711 

48.60 

41.15 

.93473 

49.85 

42.32 

.93934 

47.40 

40.04 

.93702 

48.65 

41.20 

.93463 

49.90 

42.37 

.93925 

47.45 

40.08 

.93692 

48.70 

41.24 

.93454 

49.95 

42.41 

.93916 

47.50 

40.13 

.93683 

48.75 

41.29 

.93906 

47.55 

40.18 

.93679 

48.80 

41.34 

.93898 

47.60 

40.22 

.93664 

48.85 

41.38 

.93888 

47.65 

40.27 

.93655 

48.90 

41.43 

.93879 

47.70 

40.32 

.93645 

48.95 

41.47 

SECTION  XII 
DETECTION  OF  COAL-TAR  DYE 

The  use  of  coal-tar  dyes  in  food  and  drink,  while  very 
general,  is  quite  unnecessary,  and  frequently  constitutes 
fraudulent  adulteration.  These  dyes  can  usually  be  de- 
tected by  the  following  methods: 

Double-Dyeing  Process.  Sostegni  and  Carpentieri.  If  a 
solid  or  semisolid,  dissolve  10  to  20  g.  of  the  sample  in 
100  cc.  of  water.  If  a  liquid,  use  from  50  to  100  cc.,  depend- 
ing upon  the  intensity  of  the  color.  Acidify  with  2  to  4  cc. 
of  10  per  cent  HC1.  Boil  nun's  veiling  or  other  white 
woolen  cloth  in  very  dilute  KOH  or  strong  soapsuds  and 
wash  thoroughly.  Boil  a  piece  about  10  cm.  square  in  the 
dissolved  sample  until  it  has  been  well  colored.  This  usually 
takes  from  five  to  ten  minutes. 

Remove  the  cloth,  wash  in  cold  water,  and  boil  in  2  per 
cent  HC1.  After  thorough  rinsing  dissolve  the  color  in  hot 
dilute  NH4OH  (1  to  50).  Remove  the  cloth  and  throw 
it  away. 

Add  a  slight  excess  of  HC1  to  the  ammonia  solution.  Im- 
merse in  this  a  second  and  smaller  piece  of  cloth  (2x3  cm.) 
and  boil. 

If  the  dye  is  of  vegetable  origin,  the  second  piece  of  wool 
will  be  practically  uncolored  in  the  ammonia  solution ;  if 
it  is  of  coal-tar  origin,  it  will  take  a  decided  tone,  —  red, 
pink,  yellow,  green,  etc.,  —  depending  upon  the  color  of 
the  sample  tested. 

76 


DETECTION  OF  COAL-TAR  DYE  77 

Arata's  Method.  Dissolve  20  to  30  g.  of  the  sample  in 
100  cc.  of  water  and  10  cc.  of  a  10  per  cent  solution  of 
HKSO4.  In  this  mixture  boil  a  small  piece  of  cloth  which 
has  been  previously  boiled  in  dilute  NaOH  and  thoroughly 
washed  in  water.  Remove,  wash  in  water,  and  dry  between 
filter  or  blotting  papers. 

If  the  coloring  matter  is  entirely  of  vegetable  origin,  the 
wool  will  be  uncolored  or  will  take  a  faint  pink  or  brown, 
which  is  changed  to  green  or  yellow  by  ammonia  and  not 
restored  by  washing. 

In  addition,  double  dye,  as  indicated  in  the  previous 
method.  If  the  wool  is  still  uncolored,  the  dye  is  of  vege- 
table origin. 

Nun's  veiling  is  a  very  suitable  cloth  for  these  experi- 
ments. In  removing  the  natural  wool  fat  many  students 
make  the  mistake  of  boiling  it  in  too  strong  caustic.  A 
1  per  cent  solution  is  sufficiently  strong. 

Cochineal  and  some  vegetable  colors  dye  wool  directly, 
hence  the  necessity  of  double  dyeing. 

Common  substances  which  furnish  excellent  material  for 
coal-tar-dye  testing  are  candy,  soft  drinks,  wine,  tablets,  jam, 
jelly,  catsup,  colored  sugars,  dessert  powders,  gelatin,  etc. 

Well-mounted  pieces  of  wool  dyed  with  these  materials 
and  placed  in  the  notebook  give  it  a  living  interest. 

Detection  of  Coal-Tar  Dye  in  Butter.  Melt  a  quantity  of 
butter  the  size  of  a  marble  in  a  test  tube,  being  careful  not 
to  scorch  it.  Add  an  equal  volume  of  Low's  reagent  and 
shake  vigorously.  Heat  nearly  to  boiling  and  set  aside. 
After  the  acid  has  settled  it  will  be  wine, red  in  the  pres- 
ence of  azo  colors.  Pure  butter  fat  gives  only  a  faint  bluish 
tinge.  (Low's  test.) 

Low's  Reagent.    HC2H3O2,  4  parts;  H2SO4,  1  part.    Mix. 


78  ELEMENTARY  APPLIED  CHEMISTRY 

Martin's  Test.  Shake  5  g.  of  the  butter  in  a  test  tube 
with  20  cc.  of  Martin's  reagent.  Let  the  mixture  stand 
until  the  fat  has  settled  to  the  bottom  of  the  tube.  The 
dye,  if  present,  will  color  the  supernatant  liquid  yellow. 

Martin's  Reagent.    CS2,  4  cc. ;  C4H5OH,  30  cc.    Mix. 

Acid  and  Alkali  Test.  Melt  about  20  g.  of  the  butter  in 
an  evaporating  dish  and  set  on  a  water  bath  until  the  curd 
and  contained  water  have  entirely  separated.  Pour  off  the 
clear,  supernatant  fat  and  filter  it  through  a  dry  filter  paper 
in  a  hot- water  funnel  or  in  an  oven  at  60°  C.  If  the  fat  is 
not  clear,  it  must  be  filtered  again. 

Pour  into  each  of  two  test  tubes  2  g.  of  this  filtered 
fat  dissolved  in  ether.  Into  one  of  the  tubes  pour  1  cc.  of 
HC1  and  into  the  other  the  same  volume  of  10  per  cent 
KOH.  Shake  the  tubes  well  and  allow  to  stand.  In  the 
presence  of  azo  dye  the  test  tube  to  which  the  acid  has  been 
added  will  show  a  pink  to  wine-red  coloration,  while  the 
alkaline  solution  in  the  other  tube  will  show  no  color.  If 
annatto  or  other  vegetable  color  has  been  used,  the  potash 
solution  will  be  colored  yellow  {Bulletin  No.  107). 

Coal-Tar  Dye  in  Lemon  Extract.  Lythgoe's  Test.  To  the 
original  sample  add  two  or  three  drops  of  strong  HC1. 

No  change  indicates  natural  color,  turmeric,  or  naphthol 
colors. 

Pink  indicates  tropseolin  or  methyl  orange. 

Partial  decoloration  indicates  Martin's  yellow. 

Complete  decoloration  indicates  dinitro-cresols. 

Evaporate  10  to  20  cc.  of  the  sample  to  dryness,  dissolve 
the  residue  in  water,  and  employ  the  test  of  Sostegni  and 
Carpentieri. 

Why  are  flavoring  extracts  often  artificially  colored  ? 


SECTION  XIII 
IDENTIFICATION  OF  VEGETABLE  COLOES 

Caramel.  Amthor's  Test.  Place  10  cc.  of  the  suspected 
solution  in  a  Nessler  tube  or  narrow  clear-glass  bottle.  Add 
from  30  to  50  cc.  of  paraldehyde,  the  latter  volume  if  the 
color  is  very  dark.  To  make  the  solutions  mix,  introduce  a 
few  cubic  centimeters  of  absolute  alcohol. 

If  caramel  is  present,  a  yellow  to  dark-brown  precipitate 
will  fall  to  the  bottom  of  the  tube. 

Fuller' s-Earth  Method.  Shake  50  cc.  of  the  solution  with 
25  g.  of  fuller's  earth.  Allow  the  mixture  to  stand  in  a 
corked  bottle  of  about  2  in.  diameter  for  an  hour  at  room 
temperature. 

The  caramel  will  be  absorbed  by  the  earth,  and  the  super- 
natant liquid  will  appear  more  or  less  clear,  depending  upon 
the  amount  of  the  absorption. 

As  some  fuller's  earth  absorbs  color  more  readily  than 
others,  it  is  advisable  to  experiment  with  different  samples 
upon  solutions  known  to  contain  caramel. 

Amyl-Alcohol  Method.  Shake  5  cc.  of  the  solution  with 
10  cc.  of  amyl  alcohol  in  a  small  vial  for  a  minute  or  so. 
Allow  the  liquids  to  separate. 

If  caramel  is  present,  the  upper  layer  will  be  decolorized 
to  a  greater  or  less  extent.  The  lower  layer  will  be  colored 
in  proportion  to  the  amount  of  caramel  in  the  solution. 

Test  vanilla  extract,  whisky,  ginger  ale,  soft  drinks,  and 
the  like  for  caramel. 

79 


80 


ELEMENTARY  APPLIED  CHEMISTRY 


Cochineal.  Grirard  and  Dupres  Method.  If  the  sample  is 
catsup,  canned  fruit,  or  of  this  nature,  triturate  in  a  mortar 
with  water  until  it  is  reduced  to  a 
very  thin  paste.  Filter,  acidulate 
with  HC1,  'and  shake  with  amyl 
alcohol.  If  cochineal  is  present,  the 
alcohol  will  be  colored  yellow  or 
orange.  Separate  the  amyl  alcohol 
and  wash  it  with  water  until  neutral. 
Add,  drop  by  drop,  a  very  dilute 
solution  of  uranium  acetate.  In  the 
presence  of  cochineal  a  beautiful 
emerald-green  color  is  produced. 

Turmeric.  Extract  the  color  with 
alcohol.  Saturate  a  filter  paper  with 
the  extract  and  dry  at  100°  C.  Dip 
the  paper  in  a  dilute  solution  of 
boric  acid  to  which  a  few  drops 
of  10  per  cent  HC1  have  been 
added.  Dry  the  paper.  Turmeric 
is  indicated  by  a  distinct  cherry-red 
coloration.  Add  a  drop  of  alkali  and  olive-green  will  de- 
velop (Bulletin  No.  51,  United  States  Bureau  of  Chemistry, 
p.  131). 


FIG.  17.   True  and  artifi- 
cial whisky  treated  with 
amyl  alcohol 

Caramel  shows  in  the  hot- 
torn  of  the  right-hand  hottie. 
The    supernatant   liquid    is 
decolorized 


SECTION  XIV 
RAFFIA  DYEING 

Raffia  is  the  cuticle  of  the  leafstalks  of  the  Madagascar 
palm  (Raffia  mffia).  Its  tissue  is  cellulose  for  the  most 
part,  so  the  method  of  dyeing  must  necessarily  differ  from 
the  method  followed  in  dyeing  wool,  silk,  or  other  animal 
fabrics. 

A  mordant  is  a  substance  to  "set"  a  color;  that  is,  to 
make  the  pigment  unite  chemically,  or  in  some  cases  physi- 
cally, or  both,  with  the  material  dyed.  The  principal  mor- 
dants used  in  raffia  dyeing  are  alum  and  other  aluminium 
salts,  and  certain  salts  of  iron,  tin,  and  copper. 

Raffia  is  soaked  in  the  mordant  solution  until  thoroughly 
impregnated,  and  then  boiled  in  a  solution  of  the  dye,  which 
forms  with  the  mordant  a  metallic  colored  substance  known 
as  a  "  lake.-'  A  lake  is  relatively  insoluble  and  cannot  be 
easily  washed  out. 

General  Principles.  Alum  should  be  used  as  a  mordant 
unless  otherwise  specified.  Dissolve  1/4  Ib.  in  10  qt.  of 
water.  Let  the  raffia  stand  in  this  solution  until  it  has 
become  thoroughly  saturated.  From  six  to  twenty-four 
hours  is  generally  sufficient.  Always  untie  the  bundles 
and  do  them  up  loosely. 

Raffia  should  not  be  dry  when  placed  in  the  dye.  Either 
take  it  directly  from  the  mordant  or  wet  it  thoroughly 
with  water.  Let  the  dye  be  boiling  when  the  raffia  is 
placed  in  it. 

81 


82  ELEMENTARY  APPLIED  CHEMISTRY 

Alum  spots,  grayish  patches  on  the  finished  product,  are 
not  generally  disadvantageous.  Most  autumn  foliage  has 
a  white  fungus  which,  in  general  appearance,  these  spots 
resemble.  A  dip  in  warm  water  will  remove  them.  Colors 
obtained  as  herein  directed  will  compare  favorably  with  the 
bright,  soft  colors  of  autumn  or  the  fresh  tints  of  spring. 

Do  not  dye  too  dark.  Lighter  tints  are  more  pleasing  in 
woven  and  braided  work.  Dye  slightly  darker  than  desired, 
as  the  raffia  is  lighter  when  dried.  Test  pieces  may  be 
quickly  dried  by  holding  them  against  the  side  of  the  hot 
dye  pan.  This  saves  time  and  affords  a  convenient  means 
of  judging  color  value. 

Strong  dye  and  short  boiling  makes  soft,  flexible,  tough 
raffia.  Weak  dye  and  long  boiling  makes  harsh,  brittle 
raffia.  Some  of  the  coal-tar  dyes  leave  the  material  glossy, 
harsh,  and  brittle.  Fifteen  minutes  should  be  the  maximum 
time  of  boiling. 

Vegetable  dyes,  in  general,  give  soft,  pleasing  tones. 
Coal-tar  dyes  give  bright,  glossy  colors. 

Rinse  before  putting  into  a  dye  of  another  color.  Dull, 
passive  colors  may  be  brightened  by  boiling  in  fresh  or 
stronger  dye.  Weak  dye  is  of  little  value.  Keep  the  raffia 
well  covered  with  dye,  and  turn  frequently. 

Dyes  extracted  from  bark,  leaves,  fruit,  roots,  vegetables, 
wood,  and  the  like  should  be  carefully  strained  before  using. 

Save  the  waste  dye,  as  many  beautiful  effects  may  be  pro- 
duced from  it.  It  is  not  only  economical  to  use  this  dye, 
but  interesting  to  discover  the  different  colors  that  may  be 
obtained. 

Time  directions  are  only  approximate,  as  much  depends 
upon  the  quality  and  strength  of  the  dye  and  on  the  kind 
and  amount  of  mordant  absorbed. 


RAFFIA  DYEING  83 

The  outer  side  of  the  raffia  will  take  a  brighter  tone  than 
the  inner  side.  This  is  especially  noticeable  in  green  and 
orange  tones. 

Do  not  place  the  full  amount  of  raffia  in  the  pan  at 
once.  Dye  a  small  piece  and  see  if  the  color  suits  you.  Do 
not  throw  away  the  material  which  is  displeasing  in  color, 
as  it  may  easily  be  dyed  black  or  brown. 

Experiment  by  mixing  small  quantities  of  various  dyes 
and  mordants  in  cups  and  test  tubes.  You  will  doubtless 
discover  some  new  and  pleasing  combination. 

Material  will  absorb  only  a  certain  amount  of  the  dye. 
This  amount  absorbed,  the  pigment  point  is  reached.  Do 
not  expect  to  pour  a  quart  of  water  at  once  into  a  pint  cup. 

Dye  pans  should  be  large  enough  for  the  work  at  hand. 
The  four-quart  or  eight-quart  size  is  convenient.  The  best 
results  are  obtained  by  using  enamel  ware. 

Preparation  of  Dyes  and  Mordants.  Dyes  and  mordants 
should  be  prepared  in  the  following  manner : 

Butternut.  Fill  a  four-quart  pan  half  full  of  the  husks ; 
green  ones  give  the  softest  tones ;  the  shells  are  not  objec- 
tionable. Cover  with  water  and  boil  for  fifteen  minutes. 

Cardinal  Red.  Dissolve  a  mass  the  size  of  a  cranberry  in 
a  gallon  of  water. 

Copper  Sulfate.    Two  ounces  to  a  quart  of  water. 

Elderberries.    Berries,  1  part ;  water,  3  parts. 

Fustic  Chips.  A  teacupful  to  4  qt.  of  water.  Boil  ten 
minutes. 

Fustic  Extract.  Dissolve  a  piece  the  size  of  a  walnut  in  a 
gallon  of  water. 

Iron  Sulfate.  Two  ounces  to  a  quart  of  water.  Always 
use  this  solution  in  an  old  dish,  as  it  will  soon  ruin  a 
new  one. 


84  ELEMENTARY  APPLIED  CHEMISTEY 

Indigo.  Use  indigo  paste  (sulfate  of  indigo).  Dissolve  a 
mass  the  size  of  two  shoe  buttons  in  4  qt.  of  water. 

Logwood  Chips.    See  Fustic  Chips. 

Logwood  Extract.    See  Fustic  Extract. 

Leaves.  Fill  a  four-quart  pan  full  of  the  shredded  leaves 
well  pressed  down.  Cover  with  water,  and  boil.  Replenish 
the  water  from  time  to  time  until  the  dye  appears  highly 
colored.  The  usual  time  is  about  fifteen  minutes. 

Onion  Skins.  The  outer  skins  from  half  a  dozen  medium- 
sized  onions  will  furnish  yellow  dye  for  half  a  pound  of 
raffia.  Boil  until  the  color  is  extracted.  The  time  required 
is  about  ten  minutes. 

Potassium  Ferri-cyanide  (Red  Prussiate  of  Potash').  Two 
ounces  to  a  quart  of  water. 

Potassium  Bichromate.  Dissolve  1  oz.  in  a  quart  of  water. 
This  solution  used  with  red  dulls  it  and  gives  an  orange 
tone. 

Sumac.  Three  quarts  of  the  broken  cones.  Keep  well 
covered  with  water  and  boil  for  twenty  minutes. 

Walnut.    See  Butternut. 

Specific  Directions  for  obtaining  the  Following  Colors : 

Black.  1.  Dye  heavily  with  logwood  and  place  imme- 
diately, without  rinsing,  into  a  strong,  hot  FeSO4  solution. 

2.  Dye  as.  above,  substituting  oak  leaves  for  the  logwood. 

Blue.  Dye  unmordanted  raffia  in  indigo  solution  to  which 
two  or  three  drops  of  H2SO4  have  been  added.  Dry  in 
direct  sunlight.  The  brighter  the  light,  the  bluer  the  color. 
Many  tones  can  be  produced  by  dyeing  for  different  lengths 
of  time  in  this  solution. 

Blue-Green.  1.  Boil  mordanted  raffia  in  plain  indigo  solu- 
tion and  dry  away  from  the  sunlight.  Raffia  dyed  with  indigo 
must  be  thoroughly  rinsed  to  remove  all  traces  of  acid. 


KAFFIA  DYEING  85 

2.  Dye  in  potassium  ferri-cyanide  to  which  a  few  drops 
of  H2SO4  have  been  added  and  mixed  thoroughly. 

3..  Dye  as  in  2,  and  place  directly  into  hot  iron  sulfate. 

Brown.  1.  Boil  in  dye  from  maple  leaves  until  thoroughly 
colored.  Remove,  rinse,  and  wring  out  the  superfluous 
liquid.  Then  boil  in  a  dye  prepared  as  follows :  Strong 
butternut  dye  to  which  has  been  added  1/2  pt.  of  K2Cr2O7 
solution  and  an  equal  amount  of  cardinal-red  solution. 

2.  First  dye  in  redwood  solution  and  immerse  for  about 
three  minutes  in  hot,  strong  logwood. 

Light  Brown.    1.  Boil  in  clear  butternut  dye. 

2.  Boil  in  clear  maple  dye. 

3.  Dye  green  with  fustic  and  indigo,  q.v.,  and  then  boil 
in  a  solution  of  CuSO4. 

Chocolate-Brown.    Dye  in  sumac  and  treat  with  FeSO4. 

Dark-Brown.    Boil  in  butternut  and  then  in  K2Cr2O?. 

Gray-Brown.  Equal  amounts  of  sumac,  maple,  and  oak 
leaves  make  a  green-brown  dye.  Since  red  is  the  comple- 
ment of  green,  and  combined  with  it  makes  gray,  add 
sufficient  logwood  to  bring  to  the  desired  shade. 

Olive-Brown.  Boil  for  six  minutes  in  dye  from  walnut 
husks. 

Red-Brown.  1.  Add  a  teaspoonful  of  alum  to  walnut 
dye  and  boil  in  the  resulting  solution  for  ten  minutes. 

2.  Dye  with  cardinal  and  then  with  logwood. 

3.  (a)  Dye  in  redwood  solution. 

(6)  Then  dye  in  a  solution  made  from  fustic  chips,  3  parts, 
and  logwood  chips,  1  part. 

Yellow-Brown.  Boil  first  in  a  dye  from  maple  leaves  and 
then  in  K2Cr2O?. 

Green.  Bright  Gf-reen.  Dye  yellow  with  fustic  and  onion 
skins.  Place  immediately  in  a  strong,  hot  solution  of 


$6  ELEMENTARY  APPLIED  CHEMISTRY 

indigo.  Dull  with  iron  sulf  ate  to  the  desired  shade.  Nearly 
all  tones  can  be  produced  by  this  method. 

Dull  G-reen.    Dye  with  black  birch  leaves. 

Dark  Green.    Dye  with  the  birch  and  dip  into  FeSO4. 

Gray-  G-reen.  Add  sufficient  ammonia  to  elderberry  juice 
to  turn  it  a  pronounced  green.  Boil  the  raffia  in  this  solu- 
tion until  the  desired  shade  is  produced.  The  time  required 
is  about  eight  minutes. 

Olive- G-reen.  See  Dark  Green.  Boil  longer  in  the  iron 
sulfate  solution.  If  left  too  long,  the  raffia  acquires  a  heavy 
olive  tone  not  pleasing  to  the  eye. 

Yellow- Green.  Color  with  fustic  or  onion  skins  and  very 
slightly  with  indigo. 

Gray.  For  these  effects  in  general,  boil  in  dye  from 
sumac  cones  with  the  stems.  A  dip  in  iron  sulfate  will 
produce  a  pleasant  neutral  effect. 

Old  Rose.  Dye  with  sumac  berries,  discarding  all  stems. 
Substitute  elderberries  for  the  sumac. 

Orange.  1.  Dye  in  fustic  and  then  in  strong,  hot  redwood 
infusion. 

2.  Boil  in  butternut  for  about  six  minutes.  Rinse  and 
dip  into  cardinal  solution. 

To  produce  a  peculiar  but  pleasing  effect,  dye  first  in 
fustic  and  then  in  cardinal.  One  side  will  be  brown  yellow, 
the  other  a  dark  red. 

Red.  With  infusions  of  redwood  it  is  possible  to  get  an 
almost  complete  color  scale,  from  a  deep,  rich,  dark  red  to 
a  pale  orange.  These  colors  can  be  dulled  with  FeSO4, 
thus  producing  an  infinite  variety  of  tints  and  shades. 

For  a  deep  red  a  very  strong  solution  is  needed,  and  only 
a  small  quantity  of  material  can  be  colored  at  a  time.  As 
the  strength  is  reduced  the  color  tends  toward  orange. 


KAFFIA  DYEING  87 

The  lighter  tints  of  orange  can  be  dulled  with  iron  sul- 
fate  to  give  a  pleasing  light  brown,  practically  identical 
with  that  produced  from  sumac. 

Bright  Red.  Dye  in  sumac  and  strengthen  in  cardinal, 
or  dye  directly  in  the  cardinal. 

Dark  Red.  1.  Dye  a  bright  red  and  dip  in  iron  sulfate. 
The  longer  it  remains  the  darker  it  becomes,  until  the  limit 
is  reached. 

2.  Dye  brown  with  waste  dye  and  then  boil  in  cardinal. 

Indian  Red.  1.  Dye  orange  red  and  boil  in  CuSO4  for 
two  minutes. 

2.  Dye  light  brown  and  boil  first  in  cardinal  solution 
and  then  in  potassium  dichromate. 

3.  To  butternut  dye  add  half  as  much  cardinal  solution, 
one  eighth  as  much  K2Cr2O7,  one  fourth  teaspoonful  of 
indigo  paste,  2  oz.  of  logwood  chips.    Boil  and  strain,  and 
dye  the  raffia  in  the  clear  liquid. 

4.  To  produce  a  pale  shade,  dye  in  an  extra  strong  solu- 
tion from  the  sumac  berries  after  discarding  the  stems. 

Purple-Red.  Dye  in  cardinal  and  then  in  indigo,  or  dye 
alum-mordanted  raffia  in  logwood. 

Yellow.  Any  of  the  yellow  tones  may  be  intensified  by 
longer  boiling. 

Lemon  Yellow.  1.  Boil  in  dye  from  pear  leaves  to  which  a 
spoonful  of  alum  has  been  added.  Alum  intensifies  the  color. 

2.  Boil  for  one  minute  in  fustic,  or  for  the  same  length 
of  time  in  onion  skins. 

Any  of  the  colors  herein  described  can  be  duplicated, 
provided  the  experimenter  becomes  familiar  with  the  special 
dye  at  hand. 

Raffia  dyeing  is  not  merely  a  mechanical  process ;  it  is 
an  art  learned  best  by  the  patient  and  orderly  worker. 


SECTION  XV 

CHEMISTRY  OF  STAINS 

A  stain  may  be  caused  by  the  union,  chemical  or  physi- 
cal, or  both,  of  some  substance  with  a  suitable  medium,  as 
paper,  cloth,  skin,  and  the  like.  The  subject  is  a  very  deep 
and  intricate  one. 

When  a  stain  is  purely  physical,  as,  for  example,  a  spot 
of  grease  on  cloth,  physical  means  of  removing  it  are  best ; 
that  is,  some  simple  process  of  absorption  or  solution. 

When  the  stain  is  of  a  chemical  nature  and  certain  oxids 
are  formed,  —  take,  for  example,  the  stain  of  apple  juice  on 
cloth,  —  chemical  means  must  be  employed  to  reduce  or 
"bleach"  the  oxid. 

When  a  stain  is  of  both  a  chemical  and  physical  nature, 
both  physical  and  chemical  means  should  be  employed  to 
remove  it.  A  stain  of  this  character  may  be  illustrated  by 
an  ink  spot  on  cloth. 

A  good  general  bleaching  reagent  consists  of  a  double 
solution  kept  in  separate  bottles. 

No.  1.    Acetic  or  tartaric  acid  solution,  20  per  cent. 
No.  2.    Five  grams  of  bleaching  powder  (CaClOx).   Boil  in  100  cc. 
of  water  until  a  pink  color  appears.  Filter  and  add  50  cc.  of  cold  water. 

This  combination  is  sometimes  called  "  ink  eradicator."  It 
must  not  be  applied  to  silk  or  to  fabrics  of  delicate  color. 

To  remove  stains  of  ink,  coffee,  tea,  fruit,  and  dye,  wet 
the  spot  thoroughly  with  No.  1.  Absorb  the  superfluous 
liquid  with  a  blotter  and  apply  No.  2.  Rinse  and  repeat, 

88 


CHEMISTRY  OF  STAINS 


89 


if  necessary.  If  a  persistent,  yellowish  spot  remains,  as  is 
•often  the  case  when  woolen  goods  have  been  treated, 
remove  all  traces  of  the  reagents  and  saturate  with  fresh 
H2O2.  Common  stains  may  be  removed  by  treating  as 
shown  in  the  following  table : 


STAIN 


REMOVED  BY 


Acids  .  .  .  . 
Grass  and  fruit 
Grease 


Dyes,  coal-tar  or  of  vege- 
table origin    .... 
Mildew    ...... 

Inks 

Inks,  indelible  (silver)    . 


lodin 

Iron  rust 

Paint,  varnish  .... 
Tar,  wagon  grease      .     . 


Cold  water,  Nos.  1  and  2 

Cold  water,  alcohol,  Nos.  1  and  2 

Gasoline,  carbon  tetrachlorid,  chloroform, 
ether,  carbon  bisulfid,  ammonia,  soapsuds, 
warm  fuller's  earth  (cover  with  a  blotter 
and  apply  a  warm  flatiron) 

Nos.  1  and  2,  ammonia 

Nos.  1  and  2,  sunlight 

Nos.  1  and  2 

Potassium  cyanide,  10  per  cent.    Use  great 

caution,  intensely  poisonous.   Sodium  hypo- 

sulfite,  20  per  cent 
Methyl    alcohol,    potassium    iodid    solution, 

10  per  cent 
Warm  oxalic  or  citric  acid,  10  per  cent.   If  in 

silk,  let  it  alone 
Turpentine,  benzine,  carbon  tetrachlorid.  Use 

no  turpentine  on  silk 
Soap  and  oil,  turpentine 


SECTION  XYI 


FOOD  PKESERVATIVES. 

Detection  of  Sulfurous  Acid.  Weigh  about  25  g.  of  the 
sample  into  a  200-cc.  Erlenmeyer  flask.  Add  water,  if  nec- 
essary, to  form  a  thin  paste 
and  about  5  g.  of  sulfur-free 
zinc.  Introduce  10-20  cc. 
chemically  pure  HC1.  Over 
the  mouth  of  the  flask  place 
a  small  filter  paper  which 
has  been  wet  with  a  strong 
solution  of  Pb  (NO8)2.  Heat 
gently.  The  blackening  of 
the  filter  paper  indicates  the 
presence  of  sulfites.  Why  ? 
A  mere  browning  of  the  filter 
paper  should  not  be  accepted 
as  evidence  of  the  inten- 
tional addition  of  SO2,  either 
as  a  preservative  or  as  a 
bleaching  agent ;  it  must  be 
distinctly  black.  (Bulletin 
No.  107,  p.  187.) 

Distillation  Method.  Leach. 
Reduce    100-200  g.    of    the 
sample   to   paste   as  before, 
and    acidify   with    5  cc.    of 
90 


FIG.  18.    Apparatus  arranged   for 

the  detection  of  sulfurous  acid  by 

the  distillation  method 


FOOD  PRESERVATIVES  91 

20  per  cent  phosphoric  acid.  Transfer  to  a  boiling  flask  and 
distil.  Arrange  the  apparatus  so  that  the  outlet  of  the  con- 
denser will  dip  below  the  surface  of  a  little  water,  about  20  cc. 

Distil  off  20  to  30  cc.  Treat  the  distillate  with  5  to  10  cc. 
of  bromin  water  and  boil  for  a  minute  or  so. 

Without  waiting  for  the  distillate  to  cool,  add  a  little 
BaCl2.  A  white  precipitate  indicates  sulfurous  acid. 

What  is  this  precipitate  ?  Test  its  solubility.  Of  what 
use  is  the  bromin  water  ? 

Test  molasses,  lime  juice,  mushrooms,  Hamburg  steak, 
sausage,  etc.  for  sulfurous  acid. 

Determination  of  Sulfurous  Acid  by  Direct  Titration.  Care 
must  be  taken  in  applying  this  method  to  other  products 
than  wine  to  determine  whether  the  iodin  is  decolorized  by 
any  substance  that  may  naturally  be  present. 

Macerate  25  g.  of  the  sample,  if  a  solid  or  semisolid,  with 
sufficient  water  to  form  a  thin  paste.  Place  in  a  200-cc.  Erlen- 
meyer  flask.  Add  25  cc.  of  normal  KOH,  mix  thoroughly, 
and  allow  it  to  stand  for  fifteen  minutes,  shaking  from  time 
to  time.  Add  10  cc.  of  dilute  sulfuric  acid  (1  to  3)  and  5  cc. 
of  freshly  prepared  starch  solution.  Rapidly  titrate  the  mix- 
ture with  N/50  iodin  solution  until  a  blue  color  is  perma- 
nent for  several  minutes. 

One  cubic  centimeter  of  N/50  iodin  solution  is  equivalent 
to  0.00064  gram  of  sulfur  dioxid. 

From  the  per  cent  of  SO2  calculate  the  per  cent  of  sulfur- 
ous acid  in  the  original  sample  (Bulletin  No.  107,  p.  188). 

Detection  of  Boron  Compounds  —  Borax  or  Boric  Acids.  It 
is  not  uncommon  to  find  this  forbidden  preservative  in 
cheese,  ice-cream  cones,  fancy  crackers  and  biscuits.  It  was 
formerly  used  in  canned  meats,  but  the  practice  has  greatly 
declined  of  late. 


92  ELEMENTARY  APPLIED  CHEMISTRY 

:'  The  common  symptoms  observed  after  long-continued 
doses  of  borax  or  boric  acid  in  food  are  headaches,  sensations 
of  fullness  in  the  head,  uneasiness  and  nausea  in  the  stomach, 
and  disturbances  of  the  digestion  and  appetite"  (Wih'i/). 

Discover  the  Effects  of  H3B03  upon  Turmeric  Paper  and 
Turmeric  Tincture.  Break  about  10  g.  of  saltines  or  other 
crackers  into  a  crucible.  Add  a  pinch  of  boric  acid  or  borax, 
and  ash.  Acidulate  the  ash  with  a  drop  or  so  of  HC1  and 
dissolve  in  as  little  water  as  possible. 

(a)  Dip  a  strip  of  turmeric  paper  in  the  solution  and 
allow  it  to  dry.  Result  ? 

(6)  Mix  the  remainder  of  the  ash  solution  with  a  cubic 
centimeter  of  turmeric  tincture  in  a  watch  glass  and  evapo- 
rate over  a  water  bath.  Result  ? 

Confirm  both  («)  and  (6)  by  placing  a  drop  of  dilute 
alkali  upon  the  paper  or  on  the  contents  of  the  glass.  An 
olive-green  color  should  appear. 

After  becoming  familiar  with  the  reaction  between  boric 
acid  and  turmeric,  test  crackers  or  biscuits,  butter,  cheese, 
canned  meat,  and  shrimps  for  boron  compounds. 

Method.  Ash  about  10  g.  of  the  sample,  first  adding 
enough  limewater  to  make  an  alkaline  reaction.  Acidulate 
the  ash  with  a  drop  or  two  of  HC1.  Dissolve  in  a  few 
drops  of  water.  Test  with  the  turmeric  paper  and  with  the 
turmeric  tincture,  as  outlined. 

If  the  turmeric  is  reddened  by  the  solution  of  the  ash 
and  turned  olive-green  by  dilute  alkali,  boric  acid,  free  or 
combined,  is  present  in  the  sample. 

Boron  Compounds  in  Butter.  Melt  25  g.  of  the  sample 
on  a  water  bath  and  allow  the  aqueous  solution  to  settle. 
Decant  this  solution  and  acidulate  with  a  drop  or  so  of  dilute 
HC1.  From  this  point  apply  the  regular  turmeric  test. 


FOOD  PRESERVATIVES 


93 


Detection  .of  Salicylic  Acid  (HC7H503).  This  compound 
has  been  used  for  the  preservation  of  catsup,  jams  and 
other  fruit  products,  and  beer.  Reduce  the  sample  to  a 
thin  paste  with  water,  if  it  is  not 
already  a  liquid.  Acidify  slightly 
with  dilute  H2SO4.  Shake  with  an 
equal  volume  of  chloroform  in  a 
closed  flask  or  separatory  funnel. 
Separate  the  chloroform  and  allow 
it  to  evaporate  spontaneously. 

First  Test.  To  a  part  of  the 
dry  residue  add  a  drop  of  ferric 
chlorid  and  an  equal  volume  of 
water.  A  pronounced  violet  or 
purple  color  indicates  the  pres- 
ence of  salicylic  acid. 

Second  Test.  Heat  the  remainder 
of  the  residue  gently  with  a  few 
drops  of  20  per  qent  H2SO4  and 
a  cubic  centimeter  of  methyl 
alcohol. 

If    salicylic    acid    is    present, 

a  pronounced  odor  of  "  winter- 

FIG.  19.    Separatory    funnel 

green,"  or  methyl  salicylate,  will    for   extracting    salicylic   or 
be  apparent.  benzoic   acid  with    ether   or 

Detection'    of      Benzoic      Acid  chloroform 

.  Sublimed   crystals   of   benzoic 

(HC7H602).    Benzoic  acid  is  used    acid  show  on  the  wateh  glass. 
for  much  the    same   purpose  as 

salicylic  acid,  and  is  more  often  found  in  food  products. 
Extract  the  sample  as  for  salicylic  acid  and  evaporate 
the  chloroform.    Dissolve  a  part  of  the  dried  residue  in 
ammonia  and  evaporate  to  dryness  over  a  water  bath. 


94 


ELEMENTARY  APPLIED  CHEMISTRY 


First  Test  Dissolve  in  a  few  drops  of  water,  heating 
gently  to  effect  the  solution.  Filter  into  a  small  test  tube 
and  add  a  drop  of  ferric  chlorid.  A  flesh-colored  precipi- 
tate of  ferric  benzoate  assures  the  presence  of  benzoic  acid. 

Second  Test.  Dissolve  the 
remainder  of  the  chloroform 
extract  in  ammonia  and  evap- 
orate to  dryness  in  a  two-inch 
watch  glass.  Invert  a  second 
watch  glass  over  the  first. 
Between  these  insert  a  fil- 
ter paper  from  the  center  of 
which  has  been  cut  a  half- 
inch  circle.  Clamp  the  watch 
glasses  closely  together  and 
heat  at  a  low  temperature 
on  a  sand  bath.  If  benzoic 
acid  is  present,  needlelike 
crystals  will  sublime  on  the 
upper  watch  glass.  Examine 
them  with  a  low-power  lens. 
Dissolve  and  treat  them  with 
a  drop  of  ferric  chlorid,  as 
in  the  preceding  test. 

Detection  of  Saccharin.  Prepare  the  sample  as  for  the 
salicylic  acid.  test.  Extract  with  ether  and  allow  the  latter 
to  evaporate  at  room  temperature.  A  distinctly  sweet  taste 
indicates  the  presence  of  saccharin. 

Add  a  small  piece  of  NaOH  and  heat  gently.  The  sac- 
charin will  be  converted  into  salicylic  acid  and  can  be 
detected  by  the  ferric  chlorid  test. 


FIG.  20.    Sand   bath,   filter  paper, 

and  double  watch  glass  arranged  to 

sublime  benzoic  acid 


SECTION  XVII 

EXAMINATION  OF  TOOTH  POWDEES 

The  usual  ingredients  of  these  dentifrices  are  soap  pow- 
der, precipitated  chalk  (CaCO3),  sugar,  orris  root,  and  other 
flavoring  materials. 

Sometimes  powdered  pumice  stone  and  cuttlefish  bone  are 
substituted  for  the  chalk.  Since  these  substitutes  scratch 
the  enamel,  they  are  injurious  and  should  be  avoided.  They 
may  be  detected  as  follows : 

Shake  up  1  to  2  g.  of  the  powder  with  10  cc.  of  dilute 
alcohol.  To  the  residue  add  about  4  cc.  of  HC1  and  an 
equal  volume  of  water.  Note  any  effervescence.  Boil. 
Allow  any  undissolved  matter  to  settle  and  decant  the 
solution.  Insoluble  matter  indicates  pumice  stone.  Con- 
firm by  placing  a  little  on  a  glass  plate  and  rubbing  gently 
with  a  glass  rod.  If  pumice  is  present,  a  scratching  sound 
will  be  heard. 

Divide  the  decanted  solution  into  two  parts. 

The  First  Part.  Evaporate  to  dryness  and  test  with 
ammonium  molybdate  for  the  PO4  radical.  If  present, 
cuttlefish  bone  is  indicated. 

The  Second  Part.  Test  for  calcium  with  (NH4)2C2O4. 
Its  presence  is  indicated  by  a  flocculent  white  precipitate. 
This  further  bears  out  the  suggestion  of  the  presence  of 
powdered  bone. 


95 


96  ELEMENTARY  APPLIED  CHEMISTRY 

TABLE  OF  INDICATIONS 


EFFERVESCENCE 

RESIDUE  INSOL- 
UBLE IN  HC1 

CALCIUM 

P04 

INDICATION 

Yes 

No 

Yes 

No 

Chalk 

Yes 

No 

Yes 

Yes 

Cuttlefish  bone 

No 

Yes 

No 

No 

Pumice 

Yes 
Yes 

.  Yes 
Yes 

Yes 
Yes 

No 
Yes 

Chalk  and  pumice 
Cuttlefish   bone 

and  pumice 

What  are  the  indications  for  chalk  and  cuttlefish  bone  ? 
In  addition  to  the  above  tests,  determine  the  free  and 
combined  alkali  and  the  alkaline  carbonates. 


SECTION  XVIII 
EXPERIMENTS  WITH  GLUCOSE 

Glucose  is  widely  distributed  in  the  vegetable  kingdom. 
It  occurs  naturally  in  many  fruits  and  vegetables,  in  honey, 
in  the  blood,  liver,  and  urine.  In  the  disease  diabetes  mel- 
litus  the  quantity  present  in  the  urine  is  sometimes  as  high 
as  10  per  cent. 

It  is  artificially  prepared  on  a  large  scale  by  treating 
corn  or  potato  starch  with  dilute  sulfuric  acid.  Its  sweet- 
ness to  that  of  sugar  is  as  3  to  5.  Large  quantities  are 
annually  consumed  in  the  manufacture  of  leather,  candy, 
table  sirups,  jams,  jellies,  and  the  like. 

Conversion  of  Starch  into  Glucose.  Boil  5  to  10  g.  of 
sawdust,  filter  paper,  cotton  rags,  or  cornstarch,  with  a 
10  per  cent  solution  of  H2SO4  in  an  Erlenmeyer  flask,  in 
the  neck  of  which  is  a  funnel  to  act  as  a  reflux  condenser. 
Continue  boiling  until  the  liquid  becomes  a  decided  yellow 
or  brown.  Neutralize  with  powdered  chalk  and  filter. 
Evaporate  the  filtrate  to  a  thick  sirup. 

Suggestions.    Pour  the  acid  into  the  water. 

Flasks  will  break  if  the  starch  is  allowed  to  stick  to 
the  bottom.  For  the  first  attempt  use  corn  or  potato 
starch. 

Replenish  the  water  as  it  boils  away.  If  the  acid  becomes 
too  strong,  it  will  carbonize  the  starch. 

Neutralize  by  adding  the  chalk  well  powdered.  Test 
often  with  litmus.  Filter.  If  the  filtrate  is  still  acid,  add 

97 


98  ELEMENTARY  APPLIED  CHEMISTRY 

more  of  the  carbonate.    A  relatively  large  quantity  will 
probably  be  required. 

Add  plenty  of  water  to  the  filter  to  wash  the  glucose 
from  the  spent  carbonate. 

Great  care  must  be  taken  during  the  process  of  evapora- 
tion or  the  liquid  will  blacken.  Stir  constantly  and  finish 
over  a  water  bath. 

Reactions.  Notice  the  interesting  exhibition  of  catalysis  in 
the  following  reaction : 

C6H1006  +  H20  =  C6H1206. 

starch  glucose 

C6H1206  and  H2SO4  +  CaCO3  =  ? 

Name  the  contents  of  the  filter  paper.  Dry  it.  It  will 
keep  its  form.  Why  ?  Which  of  the  changes  in  the  above 
experiment  are  physical,  and  which  are  chemical  ? 

Test  for  Glucose  by  the  Reduction  of  a  Copper  Salt.  Dis- 
solve a  little  glucose  in  water.  Add  2  cc.  Fehling's  solu- 
tion, 1  cc.  each  of  No.  1  and  No.  2.  Heat  nearly  to  boiling. 
The  result  is  characteristic. 

Repeat,  substituting  cane  sugar  for  the  glucose.    Result  ? 

Fehling's  Solution,  No.  1 :    CuSO4,  34.6  g. ;  water,  500  cc. 
Fehling's  Solution,  No.  2  :  llochelle  salts,  173  g. ;    NaOH,  50  g. ; 
water,  500  cc.    Keep  in  separate  bottles. 

Test  for  Glucose  by  the  Precipitation  of  Dextrine.  Dis- 
solve a  little  glucose  in  water.  To  two  or  three  cubic  centi- 
meters add  a  large  excess  of  methyl  alcohol.  Agitate.  The 
glucose  is  precipitated  as  dextrine. 

Repeat,  substituting  cane  sugar  for  glucose.   Result  ? 

Inversion  of  Cane  Sugar.  Make  a  solution  of  cane  sugar 
as  before.  Add  one  drop  of  HC1  and  .boil  vigorously.  Test 
with  Fehling's  solution. 

0BHM0U  +  H20  =  C6H1206  +  C.HU0, 

oane  sugar  glucose  fructose 


EXPERIMENTS  WITH  GLUCOSE  99 

The  mixture  of  glucose  and  fructose  is  called  invert 
sugar.  Notice  how  the  inversion  is  brought  about  by  hydrol- 
ysis. Before  cane  sugar  is  digested  it  must  pass  through 
the  process  of  inversion. 

Test  honey,  confectionery,  maple  sirup,  molasses,  jam, 
jelly,  the  contents  of  pies  and  cake  fillers  for  invert  sugar 
by  the  Fehling  method. 

Test  the  same  for  glucose  by  the  precipitation  of  dextrine. 
It  is  instructive  to  treat  a  sample  of  homemade  jelly  and 
any  one  of  the  cheap  varieties  by  this  method.  A  decided 
milkiness  in  the  alcohol  indicates  commercial  glucose. 

Many  soft  candies,  waxes,  taffies,  a  large  proportion  of 
stick  candy,  caramels,  and  the  like  are  made  with  glu- 
cose. Sometimes  a  little  cane  sugar  is  added  to  give  it  a 
sweeter  taste. 

Considerable  glucose  is  used  in  the  manufacture  of  table 
sirups.  These  are  sent  to  the  market  under  euphonious 
names,  as  "Maple  Drip,"  "Bon  Ton,"  "Golden  Drip," 
"  White-Loaf  Drip,"  etc. 

Detection  of  Glucose  in  Honey.  Dissolve  one  part  of  honey 
in  an  equal  volume  of  water.  Cool  and  add  5  to  8  drops  of 
a  dilute  solution  of  iodin  in  KI. 

If  the  honey  solution  remains  a  pale  yellow,  commer- 
cial glucose  is  probably  absent.  If  decolorized,  glucose  is 
indicated. 

If  starch  is  present,  the  characteristic  blue-to-purple 
coloration  will  appear  (Beckmaris  test). 

Anilin-Acetate  Test  for  Artificial  Invert  Sugar  in  Honey. 
The  reagent  must  be  freshly  prepared.  Shake  5  cc.  of 
chemically  pure  anilin  with  5  cc.  of  water,  and  add  2  cc.  of 
glacial  acetic  acid.  The  milky  emulsion  of  anilin  and  water 
should  clear  up  perfectly  upon  the  addition  of  the  acid. 


100    ELEMENTARY  APPLIED  CHEMISTRY 

Dissolve  about  5  cc.  of  honey  in  a  test  tube  with  an  equal 
volume  of  water,  and  pour  a  little  of  the  anilin  solution 
down  the  sides  of  the  tube  so  as  to  form  a  thin  layer  upon  the 
surface  of  the  liquid.  If  artificial  invert  sugar  is  present,  a 
red  ring  will  form  beneath  this  layer,  and  on  gently  agitat- 
ing the  tube  all  of  the  acetate  will  be  tinged  this  color. 

If  the  honey  is  pure  and  has  not  been  overheated,  no 
trace  of  the  red  will  be  found. 

Sugar  in  Vegetables  and  Fruits.  Grind  a  quarter  of  a 
turnip  or  half  an  apple  through  a  food  cutter.  Place  the 
pulp  in  a  piece  of  cheesecloth  and  squeeze  the  juice  into  a 
beaker.  Taste  the  juice.  Pour  about  5  cc.  into  a  test  tube 
and  dilute  with  three  or  four  times  its  volume  of  water. 
Test  with  Fehling's  solution. 

Test  beets,  carrots,  parsnips,  etc.,  for  sugar.  How  does 
the  sugar  from  the  beet  differ  from  that  of  the  apple  ? 

Conversion  of  Starch  to  Invert  Sugar  by  the  Process  of 
Mastication.  Grind  a  few  grams  of  soda  or  milk  crackers  in 
a  mortar  with  enough  water  to  form  a  thin  paste.  Transfer 
to  a  test  tube  and  test  with  Fehling's  solution.  Result  ? 

Thoroughly  chew  about  5  g.  of  the  cracker  for  about 
one  minute.  Test  as  before.  How  do  you  account  for  the 
change  ?  Could  the  food  be  chewed  too  much  ?  Why  ? 

Detection  of  Adulteration  in  Maple  Sirup.  Coloring  Matter. 
Shake  15  cc.  of  the  sirup  with  3  cc.  of  amyl  alcohol  and 
1  cc.  of  H3PO4  (20  per  cent).  Allow  to  settle.  The  amyl- 
alcohol  layer  should  be  a  decided  brown.  Adulterated 
samples  give  a  straw-to-light-brown  color. 

Foam  Test.  Mix  5  cc.  of  the  sirup  and  10  cc.  of  water  in 
a  graduated  tube  and  shake  vigorously  for  half  a  minute. 
Allow  to  stand  ten  minutes.  The  foam  should  not  measure 
less  than  3  cc.  Adulterated  samples  give  less  foam. 


EXPERIMENTS  WITH  C4Lt(O$lt)       V  ilOl 


Precipitate  Test.  Mix  5  cc.  of  tbe  /sirup  ^ 
water  in  a  50-cc.  cylinder.  Add  2  cc.  of  lead  subacetate 
solution.  Mix  well  and  allow  to  stand  for  twenty  hours. 
The  precipitate  should  not  measure  less  than  3  cc.  (^Bulletin 
of  Pharmacy,  December,  WOS.') 

When  maple   sugar  is  to  be  tested,  dissolve   15  g.  in 
enough  water  to  make  15  cc.  of  sirup. 


SECTION  XIX 
EXAMINATION  OF  HEADACHE  POWDERS 

A  great  deal  of  injury  is  done  each  year  by  the  in- 
discriminate use  of  headache  powders,  "  cures,"  "  stops," 
tablets  for  car  sickness,  anti-pain  tablets  and  pills,  cold 
"  cures,"  and  the  like. 

Many  of  these  contain  a  coal-tar  derivative  commonly 
known  as  acetanilid,  or  antifebrin.  This  is  the  acetyl  de- 
rivative of  anilin,  and  is  therefore  called  phenylacetamid 
by  the  chemist.  This  substance  is  a  dangerous  heart  de- 
pressant and  should  never  be  used  except  by  the  intelligent 
advice  of  a  physician. 

Another  substance  frequently  used  in  cheap  powders  of 
the  above  description  is  phenacetin,  known  to  the  chemist 
as  oxyethylacetanilid.  If  one  values  his  health,  he  should 
avoid  the  common  use  of  such  pernicious  drugs. 

Detection  of  Acetanilid  in  Headache  Cures,  Cold  and  Grippe 
Powders,  and  like  Nostrums.  Strobel's  Test.  Place  about 
0.2  g.  of  the  sample  in  a  5-in.  test  tube  and  add  about 
the  same  volume  of  ZnCl2.  Heat  gently,  meanwhile  hold- 
ing a  wood  shaving  or  splint  down  the  mouth  of  the  tube. 
White  fumes  soon  appear.  Continue  heating ;  the  mixture 
melts,  turns  light  yellow  and  finally  black.  Observe  the 
shaving  from  time  to  time.  If  it  is  stained  yellow,  acet- 
anilid is  undoubtedly  present.  Note  the  peculiar  odor  of 
the  fumes.  Varnish  or  shellac  the  splint  and  mount  it  in 
the  notebook  with  the  label  from  the  package. 

102 


EXAMINATION  OF  HEADACHE  POWDEKS     103 


Ritsert's  Test.  Boil  1  g.  of  the  sample  in  a  small  beaker 
for  two  or  three  minutes  with  about  3  cc.  strong  HC1.  Cool 
and  divide  into  three  portions  and  test  in  small  tubes. 

1.  Add  carefully  1  to  3  drops  of  a  solution  of  bleaching 
powder  (CaClOx),  1  to  200,  in  such  a  manner  that  the  two 
liquids  do  not  mix.    A  beautiful  blue  color  is  seen  at  the 
junction  of  the  two  liquids 

if  acetanilid  is  present. 

This  is  known  as  the  in- 
dophenol  reaction,  and  it  re- 
sponds to  anilin  compounds 
generally. 

2.  To  another  portion  add 
a  small  drop  of  KMnO4.    A 
clear  green  color  is  formed 
if  an  appreciable  amount  of 
acetanilid  is  present. 

3.  Mix  the  third  portion 
with  a  3  per  cent  chromic  acid 
solution.    Acetanilid  gives  a 
green   color,   changing  to  a 
dark  green  in  a  few  minutes, 

and  forms  a  dark  blue  precipitate  on  the  addition  of  a  drop 
or  two  of  NaOH  solution. 

In  the  case  of  powders  containing  vegetable  matter  or 
sugar  of  milk,  both  of  which  will  turn  brown  on  heating  with 
HC1,  it  is  advisable  to  first  boil  the  sample  in  5  to  10  cc.  of 
water.  Filter,  cool  the  filtrate,  and  agitate.  If  acetanilid  is 
present,  it  will  crystallize  out  and  settle.  A  centrifuge  may 
be  used  to  advantage  to  separate  the  crystals  from  the  liquid. 
This  latter  which  still  contains  some  acetanilid  in  solution 
may  be  discarded  and  the  crystals  tested  as  indicated. 


FIG.  21.    Showing  method  of  hold- 
ing splint  for  the  Strobel  test 


104        ELEMENTARY  APPLIED  CHEMISTRY 

The  blue  color  of  the  bleaching  powder  solution  is  prob- 
ably due  to  the  presence  of  anilin  hydrochlorid. 

Test  headache  powders  for  the  bromin  radical  by  gently 
heating  with  equal  parts  of  MnO2  and  H2SO4. 

Isonitril  Reaction.  Heat  about  a  gram  of  the  powder  with 
10  cc.  of  a  10  per  cent  NaOH  solution.  Remove  from  the 
flame  and  cautiously  add  a  few  drops  of  chloroform.  Set 
aside  for  a  few  minutes.  If  acetanilid  is  present,  the  greasy, 
disgusting  odor  of  phenylcarbamine  will  be  apparent. 

This  last  test  is  perhaps  the  best  of  all,  and  is  especially 
applicable  to  a  liquid  or  solid  whose  color  might  interfere 
with  the  Ritsert  test. 

To  determine  the  Per  Cent  of  Acetanilid  present.  Dis- 
solve a  definite  weight  of  the  powder,  about  1  g.,  in  hot 
water.  Boil  and  filter.  To  the  filtrate  add  bromin  water 
until  the  yellow  color  persists.  The  acetanilid  is  precipitated 
as  p-bromacetanilid.  Dissolve  the  precipitate  in  benzol. 
Filter  and  evaporate  the  benzol  over  a  water  bath.  Dry  at  a 
temperature  not  exceeding  100°  F.  Weigh  the  residue. 

Caution.  Keep  the  benzol  from  all  flame,  as  it  is  exceed- 
ingly inflammable. 

Pure  acetanilid  melts  at  113°  C.  Determine  the  melting 
point  of  your  sample. 

If  unfamiliar  with  any  of  the  above  tests,  work  with  a 
known  sample.  Do  not  give  up  until  you  are  familiar  with 
them.  You  may  save  the  life  of  some  one. 


SECTION  XX 

TESTS  FOR  ARSENIC 

Arsenic  is  one  of  the  most  widely  distributed  elements. 
Unless  care  is  taken  by  the  manufacturer,  it  may  contami- 
nate our  foods,  articles  of  clothing,  wall  papers,  paint,  and 
the  like.  In  testing  any  such  substance  for  arsenic  it  is 
advisable  to  partially  destroy  the  organic  matter  with  a 
mixture  of  sulfuric  and  nitric  acids.  This  treatment  oxi- 
dizes the  arsenic  into  arsenic  acid,  which  may  be  completely 
removed  with  boiling  water.  The  method  advised  is  that 
of  Chittenden  and  Donaldson  (Bulletin  No.  86,  Bureau  of 
Chemistry,  United  States  Department  of  Agriculture'). 

To  successfully  perform  tests  for  arsenic,  it  is  absolutely 
necessary  that  all  of  the  reagents  are  themselves  free  from 
it.  Assure  yourself  of  this  first  of  all.  Save  time  by  putting 
a  few  scraps  of  arsenic-free  zinc  into  four  different  flasks : 

No.  1  containing  10  per  cent  HC1. 

No.  2  containing  10  per  cent  H2SO4. 

No.  3  containing  10  per  cent  nitro-sulfuric  acid. 

No.  4  containing  10  per  cent  HC1  and  a  few  drops  of 
10  per  cent  CuCl2. 

Over  the  mouth  of  each  flask  place  a  piece  of  filter 
paper,  which  has  been  wet  with  a  few  drops  of  concen- 
trated solution  of  mercuric  chlorid.  There  should  be  a 
brisk  evolution  of  gas. 

If  after  half  an  hour  the  filter  paper  shows  no  discolor- 
ation, the  reagents  are  suitable  for  use. 

105 


100         ELEMENTARY  APPLIED  CHEMISTRY 


Preparation  of  the  Sample.  Wall  Paper,  Cloth,  etc.  Place 
about  25  sq.  cm.  of  the  sample  cut  into  small  pieces  in  an 
evaporating  dish.  Treat  with  1  to  5  cc.  of  a  mixture  of  con- 
centrated sulfuric  and  nitric  acids,  30  to  1,  both  of  which 
have  been  proved  free  from  arsenic.  Add  a  few  drops  of 


EIG.  22.   Gutzeit  apparatus  for  the  detection  of  arsenic 
Showing  wash  bottle  with  outlet  capped  with  prepared  filter  paper 

water  and  allow  the  action  to  proceed  for  five  minutes. 
Heat  with  a  low  flame  until  all  of  the  acid  is  driven  off, 
or  until  the  residue  has  granulated  and  the  fumes  have 
nearly  disappeared.  Break  up  the  charred  mass,  add  a  little 
water,  and  boil  to  get  rid  of  the  H2SOg.  Filter  through  a 
small  filter  and  wash  to  about  40  cc. 


TESTS  FOB  ARSENIC 


107 


Preparation  of  the  Sample.  Meats,  Vegetables,  etc.  Heat  in 
a  porcelain  dish  about  100  g.  of  the  sample  with  23  cc.  of 
HNO3,  stirring  occasionally  with  a  glass  rod.  When  the 
substance  has  become  a  deep  yellow  or  orange  color,  remove 
from  the  heat  and  add  3  cc.  of  H2SO4.  Stir  the  contents  of 
the  dish  while  the  nitrous 
fumes  are  given  off.  Care 
should  be  taken  to  pro- 
tect the  hands  from  these 
fumes. 

Heat  gently  and  add 
while  hot,  drop  by  drop, 
8  cc.  of  HNO3,  stirring  the 
mass  constantly.  Heat 
more  strongly  until  acid 
fumes  come  off  and  a 
charred  mixture  remains. 
Break  this  up,  extract 
with  boiling  water,  and 
filter  as  in  the  case  of 
wall  paper. 

NOTE.  Always  conduct 
these  preliminary  proc- 
esses under  a  gas  hood 
or  out  of  doors. 

The  Gutzeit  Test.  Into  a  clean  Erlerimeyer  flask  of  about 
200  cc.  capacity,  fitted  with  a  thistle  tube  and  a  right- 
angled  delivery  tube,  place  a  few  pieces  of  arsenic-free 
zinc.  Slide  the  zinc  gently  into  the  flask  to  avoid  breakage. 
Pour  in  the  filtrate  from  the  prepared  sample  and  about 
5  cc.  of  the  tested  HC1,  containing  half  a  cubic  centimeter 
of  a  10  per  cent  solution  of  CuCl2  of  known  purity. 


FIG.  23.    Simple  form  of  Gutzeit 
apparatus 

Showing  the  prepared  filter  paper  held 
over  the  mouth  of  the  flask 


108         ELEMENTARY  APPLIED  CHEMISTRY 

Allow  the  escaping  gas  to  pass  through  a  few  cubic 
centimeters  of  lead  acetate  solution  contained  in  a  small 
wash  bottle  or  potash  bulb,  and  impinge  upon  a  piece  of 
Swedish  filter  paper  which  has  been  wet  with  a  drop  or  so 
of  a  concentrated  solution  of  mercuric  chlorid. 

If  after  half  an  hour  the  paper  shows  a  stain  yellow 
to  deep  orange,  arsenic  is  present.  The  color  varies  with 
the  amount.  Very  large  quantities  produce  a  yellowish- 
brown  stain. 

Write  the  reaction  between  free  hydrogen  and  arsenic. 
What  compound  causes  the  yellow  color  on  the  filter  paper  ? 
If  the  filter  paper  remains  white,  freedom  from  arsenic  is 
assured. 

Place  a  little  chemically  pure  10  per  cent  HC1  upon  per- 
fectly pure  zinc.  Result  ?  Then  add  a  few  drops  of  CuCl2 
solution.  How  do  you  explain  the  effect?  Why  was  the 
copper  chlorid  solution  added  to  the  original  sample  ? 

Make  arsenic  tests  upon  the  following :  wrapping  paper, 
samples  of  cloth,  candy  wrappings,  wall  paper,  etc.  Liquids 
can  usually  be  tested  without  subjecting  them  to  the  pre- 
vious preparation. 


SECTION  XXI 
METHOD  FOR  TESTING  PAINT  AND  OILS 

If  one  desires  to  paint  his  building  with  a  lead  and  zinc 
paint  and  pays  the  price,  he  should  get  lead  and  zinc,  not 
sand,  lime,  and  barium  sulf ate  or  barytes.  On  the  other  hand, 
if  he  pays  a  sand-and-lime  price,  he  should  not  expect  to  get 
a  metallic  article.  Which  kind  have  you  seen  used  ? 

Extraction  of  the  Oil.  Place  about  5  g.  of  the  paint  in 
a  small  flask  or  beaker  and  wash  with  successive  portions 
of  warm  petroleum  ether,  or  benzine.  Heat  this  in  a  water 
bath,  away  from  any  flame.  Continue  the  washing  until  a 
few  drops  leave  no  residue  011  evaporation. 

It  is  more  convenient  to  conduct  the  extraction  with  a 
Soxhlet  apparatus,  placing  the  paint  in  an  extraction  shell 
the  weight  of  which  must  be  previously  determined.  Dry 
the  undissolved  residue  at  100°  C.  and  calculate  the  per 
cent  of  the  oil. 

To  test  the  Purity  of  the  Oil.  Evaporate  the  ether  extract 
from  the  previous  experiment.  Warm  2  cc.  of  the  oil  so 
obtained  in  a  test  tube  and  add  an  equal  volume  of  glacial 
acetic  acid.  Cool  in  running  water  and  add  one  drop  of  con- 
centrated H2SO4.  Pure  linseed  oil  turns  sea-green,  the  color 
deepening  on  standing.  A  fugitive  violet  color  indicates 
rosin  oil. 

Heat  a  little  of  the  oil  in  a  test  tube  to  about  100°  C. 
Cool  and  rub  on  the  back  of  the  hand.  If  present,  fish  oil 
will  be  detected  by  the  characteristic  fishy  odor. 

109 


110         ELEMENTARY  APPLIED  CHEMISTRY 

To  test  the  Body  of  the  Paint.  1.  Boil  a  portion  of  the 
residue  with  strong  acetic  acid.  A  residue  indicates  BaSO4 
or  sand  (SiO2),  or  both.  Save  the  nitrate. 

2.  To  a  second  portion  add  an  equal  volume  of  Na2COg, 
then  mix  and  fuse  with  a  blowpipe  on  charcoal.    If  lead  is 
present,  a  small  metallic  globule  will  fuse  out.    Lead  in 
paint  is  usually  present  in  the  form  of  basic  lead  carbonate, 
2PbCO3-Pb(OH)2. 

3.  Moisten  a  third  portion  with  a  solution  of  Co  (NO3)2. 
Heat  strongly   as    before.    A  green   color   indicates  zinc. 
Probably  ZnO  is  in  the  original  paint. 

4.  To  the  nitrate  from   1   add    an   excess   of  NH/HI 
and  then  ammonium  oxalate.    If  lime  is  present,  a  white 
precipitate  of  oxalate  of  lime  is  formed. 

Suggest  a  method  for  determining  how  much  of  each 
ingredient  is  present. 

Test  for  the  Purity  of  Olive  Oil.  Shake  equal  volumes 
(5  cc.)  of  the  oil  and  HNO3.  Pure  oil  should  turn  from 
pale  to  dark  green  in  a  few  minutes.  If  it  changes  to  brown, 
red,  or  orange,  the  addition  of  a  foreign  oil  is  indicated. 

Heat  for  five  minutes  in  a  water  bath  at  100°  C.  It  should 
become  pale  yellow  to  orange  yellow.  On  standing  it  will, 
if  pure,  become  a  yellow  solid.  (LeacKs  test*) 

Free  Fatty  Acids  in  Olive  Oil.  Weigh  exactly  20  g.  of 
the  sample  into  a  counterpoised  Erlenmeyer  flask  and  add 
50  cc.  of  neutral  alcohol.  Mix  thoroughly  and  heat  the 
contents  to  60°  C. 

Titrate  with  tenth-normal  sodium  hydrate,  using  phe- 
nolphthalein  as  an  indicator.  Shake  the  mixture  often  dur- 
ing the  titration.  The  number  of  cubic  centimeters  of  the 
alkali  used"  to  neutralize  the  acid  in  1  g.  of  the  oil  is  called 
the  Acid  Number. 


METHOD  FOE  TESTING  PAINT  AND  OILS     111 


Each  cubic  centimeter  of  tenth-normal  sodium  hydrate 
equals  0.0282  g.  of  oleic  acid.  Tabulate  the  results  as  Acid 
Number  and  also  as  Per  Cent  of  Oleic  Acid. 

The  fresher  and  better  grades  of  olive  oils  contain  the 
least  amount  of  free  fatty  acid. 

Neutral  Alcohol.  Titrate  any  convenient  volume  of  95  per  cent  alco- 
hol with  tenth-normal  alkali,  using  phenolphthalein  as  an  indicator. 

BACH'S  TABLE  FOR  OIL  REACTIONS 


AFTER  HEATING 

CONSISTENCY 

KIND  OF  OIL 

AFTER  AGITATION 

WITH   HNO3 

FOR  FIVE  MINUTES 
ON  WATER  BATH 

AFTER  STANDING 
TWELVE  TO 

EIGHTEEN  HOURS 

Olive     .... 

Pale  green 

Orange  to  yellow 

Solid 

Peanut       .     .     . 

Pale  rose 

Brownish  yellow 

Solid 

Rape     .... 

Pale  rose 

Orange  yellow 

Solid 

Sesame      .     .     . 

White 

Brownish  yellow 

Liquid 

Sunflower       .     . 

Dirty  white 

Reddish  yellow 

Buttery 

Cottonseed     .     . 

Yellowish  brown 

Reddish  brown 

Buttery 

Castor  .... 

Pale  rose 

Golden  yellow 

Buttery 

Detection  of  Cottonseed  Oil  in  Olive  Oil.  Take  any  con- 
venient volume  of  CS  in  which  1  per  cent  of  sulfur  has 
been  previously  dissolved,  and  add  an  equal  volume  of 
amyl  alcohol  (fusel  oil). 

To  5  cc.  of  the  sample  add  an  equal  volume  of  the  re- 
agent. Stop  the  test  tube  loosely  with  cotton  and  heat  for 
fifteen  minutes  in  a  bath  of  saturated  boiling  brine. 

If  cottonseed  oil  is  present,  a  deep  red  to  orange  color  is 
developed.  Pure  olive  oil  gives  little  or  no  color  under  this 
treatment.  (Halphen  test.) 

This  test  can  also  be  used  for  the  detection  of  cottonseed 
oil  in  lard.  The  fat  from  animals  fed  on  cottonseed  meal  is 
said  to  give  a  faint  reaction. 


112         ELEMENTARY  APPLIED  CHEMISTRY 

If  the  olive  oil  containing  cottonseed  oil  has  been  pre- 
viously heated,  the  reaction  is  much  less  delicate. 

Kapok  oil,  from  the  seeds  of  the  Eriodendron  anfractuo- 
sumj  and  baobab  oil  give  the  same  reaction.  A  distinction 
can,  however,  be  made,  since  the  two  last  oils  react  without 
heating,  while  cottonseed  oil  must  be  heated. 

To  distinguish  Renovated  from  Creamery  or  Dairy  Butter. 
Melt  two  or  three  grams  of  butter  in  an  iron  spoon.  Pure 
butter  melts  quietly  with  the  production  of  much  foam. 
Renovated  butter  and  oleomargarine  bump  and  sputter  like 
hot  grease  and  produce  no  foam  to  speak  of. 

Waterhouse  Test  for  Oleomargarine.  Thoroughly  shake 
50  cc.  of  sweet  milk  and  heat  nearly  to  boiling.  Add  from 
2  to  5  g.  of  the  sample  and  stir  with  a  small  wooden  stick 
flattened  at  one  end  until  the  fat  is  entirely  melted. 

Place  the  beaker  in  a  dish  of  ice  water  and  continue 
stirring  until  the  fat  solidifies. 

If  the  sample  is  oleomargarine,  the  fat  can  be  collected 
into  a  lump.  Butter  fat  cannot  be  so  collected,  but  is  more 
or  less  emulsified  with  the  milk. 

If  the  sample  is  renovated  butter,  it  will  tend  to  collect 
as  a  film  on  the  surface  of  the  milk  when  the  stirring  is 
stopped.  It  does  not  clot  or  gather  like  oleomargarine,  but 
usually  adheres  to  the  wooden  rod. 


SECTION  XXII 
DETEEMINATION  OF  FOOD  VALUES 

Total  Nitrogen  and  Proteids  of  Cereal  Products.  Gunning's 
Method.  This  method  consists  in  decomposing  the  organic 
matter  by  prolonged  digestion  with  sulfuric  acid  and  potas- 
sium sulfate.  The  carbon  is  driven  off  as  CO2  and  the 
hydrogen  as  water.  The  nitrogen  is  converted  into  am- 
monium sulfate  from  which  the  free  ammonia  is  liberated 
by  means  of  an  alkali  and  distilled  into  a  known  volume 
of  N/10  acid,  and  the  amount  calculated  by  titrating  the 
acid  remaining. 

It  should  be  observed  that  foods  in  their  natural  state 
seldom  if  ever  contain  nitrates.  Should  this  radical  be 
present  in  appreciable  amounts,  the  Gunning  method  must 
be  modified. 

Prove  the  absence  of  nitrates  by  extracting  about  5  g. 
of  the  sample  with  water.  Filter  and  test  the  filtrate  by 
mixing  with  a  solution  of  ferrous  sulfate.  Add  concentrated 
sulfuric  acid  so  as  to  form  a  layer  below  the  mixed  solution. 
In  the  presence  of  nitrates  a  dark  brown  ring  forms  at  the 
juncture  of  the  two  liquids. 

Prove  the  reliability  of  this  reaction  by  working  with  a 
solution  known  to  contain  a  nitrate. 

In  the  absence  of  nitrates  proceed  with  the  Gunning 
method  as  follows : 

Weigh  exactly  0.5  g.  of  the  finely  powdered  sample  — 
bread,  macaroni,  breakfast  food,  etc.  —  and  transfer  to  a 

113 


114         ELEMENTARY  APPLIED  CHEMISTRY 


clean,  dry  Kjeldahl  flask  of  about  250  cc.  volume.  Add 
10  g.  of  K28O4  and  from  15  to  25  cc.  concentrated  H2SO4. 
Incline  the  flask  at  an  angle  of  about  75°  over  a  small  bare 
flame  and  heat  gently  until  all  foaming  stops. 

The  mixture  is  now  of  a  dark  brown  color.  Slip  a  piece 
of  wire  gauze  under  the  flask  and  slightly  increase  the  heat 

until  the  gauze  is  cherry  red 
where  it  comes  in  contact 
with  the  bottom  of  the  flask- 
Place  a  funnel  in  the 
neck  of  the  flask  to  act  as  a 
reflux  condenser.  Continue 
heating  until  the  contents 
are  colorless  or  of  a  pale 
straw  color.  This  usually 
takes  from  thirty  minutes 
to  two  hours.  Conduct  the 
heating  in  a  gas  hood. 

Allow  the  flask  to  cool. 
Transfer  the  liquid  into  a 
boiling  flask  of  about  500  cc. 
capacity,  rinsing  carefully 
with  200  cc.  of  water. 

Add  sufficient  saturated 
solution  of  NaOH  to  make 
the  contents  strongly  alkaline,  using  phenolphthaleiii  as 
an  indicator. 

Place  two  or  three  pieces  of  zinc  in  the  boiling  flask  to 
prevent  bumping,  and  distil  off  at  least  150  cc.,  using  a  ver- 
tical condenser  whose  outlet  dips  below  the  surface  of  ex- 
actly 50.  cc.  of  N/10  H2SO4  contained  in  the  receiving  flask. 
(See  apparatus  for  the  detection  of  sulfurous  acid.) 


FIG.  24.  Kjeldahl  flask  arranged  for 
the  determination  of  nitrogen 


DETERMINATION  OF  FOOD  VALUES          115 

It  is  of  the  utmost  importance  to  know  the  exact  volume 
of  standard  acid  in  the  receiving  flask.  Measure  with  an 
accurate  pipette. 

When  all  the  ammonia  has  been  distilled  and  absorbed, 
titrate  the  contents  of  the  receiving  flask  with  N/10  NaOH, 
using  cochineal  as  an  indicator. 

The  difference  between  the  original  volume  of  the  stand- 
ard acid  and  the  volume  of  N/10  NaOH  required  to  titrate 
it  represents  the  number  of  cubic  centimeters  of  N/10  H2SO4 


FIG.  25.  Digesting  shelf  for  making  simultaneous  nitrogen  determinations 

neutralized  by  the  liberated  ammonia.  Every  cubic  centi- 
meter of  N/10  sulfuric  acid  represents  .0014  g.  of  nitrogen. 
The  proteids  are  calculated  from  the  total  nitrogen  by 
multiplying  by  the  factor  6.25.  This  factor  is  the  one 
generally  adopted  in  determinations  of  this  kind. 

EXAMPLE.  Weight  of  cereal  —  0.5  g. 
Volume  of  N/10  H2SO4  =  50  cc. 

Required  44  cc.  of  N/10  NaOH  to  titrate  the  excess  acid. 
Therefore  6  cc.  of  N/10  II2S()4  were  neutralized  by  the  liberated 
ammonia. 

1  cc.  of  N/10  H2SO4  =  .0014  g.  of  nitrogen. 
6  cc.  of  N/10  H2SO4  =  6  X  .0014,  or  .0084  g.  of  nitrogen. 
6.25  x  .0084  =  .0525  g.  of  proteid. 

.0525/.5  =  10.5  per  cent  of  proteid. 

In  such  an  analysis  as  the  preceding  one  it  is  customary 
to  state  that  the  Protein  =  6.25  x  N. 


116         ELEMENTARY  APPLIED  CHEMISTKY 


Fat  of  Cereal  Products,  known  as  "  Ether  Extract. " 
Weigh  from  2  to  3  g.  of  the  sample  into  a  tared  extraction 
shell  (Schleicher  and  Schull).  Dry  thoroughly  at  212°. 

Place  the  shell  in  a  Soxhlet  or  Wiley  Extractor  and 
extract  with  water-free  ether.  Dry  the  shell  and  residue  to 

constant  weight  and  by  differ- 
ence calculate  the  ether-soluble 
matter. 

A  thorough  extraction  re- 
quires several  hours.  Great 
caution  must  be  exercised  in 
heating  the  extracting  appara- 
tus lest  the  ether  take  fire. 
Use  a  large  water  bath  and  a 
small  flame,  or,  still  better,  an 
electric  stove. 

Water  or  Moisture  in  Cereal 
Products.  Weigh  from  2  to  5  g. 
of  the  sample  into  a  tared  watch 
glass.  Spread  it  evenly  over  the 
bottom,  forming  as  thin  a  layer 
as  possible.  Dry  at  100°  C.,  cool, 
and  reweigh.  Calculate  the  per 
cent  of  water  by  difference. 

Ash  or  Mineral  Content  of 
Cereal  Products.  Transfer  the 
dried  residue  from  the  water  determination  to  a  tared  porce- 
lain crucible,  taking  care  that  none  of  the  sample  is  lost. 
Burn  to  a  white  ash  at  the  lowest  temperature  possible.  If 
too  much  heat  is  employed,  the  ash  will  fuse  to  the  bottom 
of  the  crucible.  Cool  in  a  desiccator,  reweigh,  and  calculate 
the  per  cent. 


FIG.  26.   Soxhlet  extraction  ap- 
paratus properly  set  up 


DETERMINATION  OF  FOOD  VALUES         117 

Carbohydrates  in  Cereal  Products.  The  carbohydrates  are 
often  expressed  by  adding  the  per  cent  of  water,  ash,  pro- 
teids,  and  fat,  and  subtracting  the  sum  from  100. 

Calculation  of  Fuel  Value.  This  value  may  be  approxi- 
mately determined  by  means  of  the  Rubner  factors,  which 
give  for  each  pound  of  protein  or  carbohydrate  1860  calories, 
and  for  each  pound  of  fat  4220  calories. 

EXAMPLE.    Suppose  the  analysis  of  a  certain  cereal  product  shows  : 
protein,  13.4  per  cent ;  carbohydrates,  74.1  per  cent ;  fat,  0.9  per  cent. 
Then  1860  x  (.134  +  .741)  =  1627.50  calories 

4220  x  .009  =     37.98  calories 
Total  1665.48 


SECTION  XXIII 
TESTING  UKINE1 

Determine  Reaction.  Normal,  slightly  acid ;  after  a  full 
meal  may  be  alkaline. 

Determine  Odor.    Normal,  peculiar,  aromatic. 

Determine  Color.  Normal,  pale  straw  to  reddish  yellow. 
May  be  very  pale  by  nervousness  or  excessive  drinking. 

Determine  Specific  Gravity.  Normal,  1.015  to  1.025  at 
60°  F. 

Determine  Total  Solids.  Normal,  3.4  per  cent  to  5.8  per 
cent.  Total  solids  equal  (specific  gravity  —  1)  multiplied 
by  2.33.  This  is  equivalent  to  the  number  of  grams  per 
cubic  centimeter. 

To  detect  Albumen  and  Phosphates.  First  Method.  Fill  a 
test  tube  half  full  of  clear  urine.  Boil  the  upper  portion 
of  the  liquid.  A  turbidity  indicates  'albumen  or  PO4,  or 
both.  Add  a  drop  of  acetic  or  nitric  acid ;  the  phosphates 
dissolve,  the  albumen  does  not. 

Second  Method.  Place  about  a  cubic  centimeter  of  con- 
centrated HNO8  in  a  test  tube,  and  by  means  of  a  pipette 
allow  two  or  three  cubic  centimeters  of  the  urine  to  rest 
upon  its  surface. 

If  albumen  is  present,  a  white  zone  or  flocculent  pre- 
cipitate forms  at  the  ring  of  contact  of  the  two  liquids. 
The  extent  of  turbidity  indicates  roughly  the  amount  of 
albumen  present. 

1  For  more  complete  analysis  see  Merck's  Manual  for  1911. 
118 


TESTING  URINE  119 

A  green  turbidity  indicates  biliary  pigments.  Reddish 
brown  indicates  blood. 

Urates  or  Uric  Acid.  Murexide  Test.  Evaporate  a  few 
drops  of  urine  to  dryness  on  a  watch  glass.  Add  a  drop  or 
two  of  HNO3  and  again  cautiously  evaporate.  Then  add 
an  equal  volume  of  NH4OH.  A  purple  color  indicates 
urates,  uric  acid,  or  both. 

Invert  Sugar.  Fehling's  Test.  Boil  5  cc.  of  Fehling's 
solution,  and  if  the  color  does  not  change,  add  an  equal 
volume  (not  more)  of  urine,  and  boil.  In  the  presence  of 
reducirig  sugars  the  characteristic  red-to-yellow  precipitate 
forms.  (See  tests  for  glucose.)  Use  this  test  only  when 
uric  acid  is  absent. 

Haines's  Test.  Reagents:  CuSO4,  2g.;  glycerin,  20  g.; 
KOH,  9  g. ;  water,  175g.  Boil  4  cc.  of  the  solution  and 
add  6  to  10  drops  (not  more)  of  the  urine  and  boil  again. 
In  the  presence  of  reducing  sugars  the  yellow-to-red  pre- 
cipitate forms. 

Detection  of  Sugar  in  the  Presence  of  Urates  or  of  Uric 
Acid.  Heat  1  g.  of  phenyldrazine  hydrochlorate,  2  g.  of 
sodium  acetate,  and  25  cc.  of  urine,  and  if  the  salts  do  not 
completely  dissolve,  add  a  little  water,  and  place  in  boil- 
ing water. 

Remove  after  twenty  minutes  to  cold  water.  If  sugar  is 
present,  characteristic  crystals  of  phenylglucosazone  form. 

Chlorids.  Add  a  few  drops  of  nitric  acid  to  the  urine 
to  prevent  the  precipitation  of  the  phosphates,  and  gradu- 
ally add  a  few  drops  of  AgNO3.  A  white  precipitate  solu- 
ble in  ammonia  indicates  chlorids.  If  present  in  small 
quantity,  a  milky  color  only  will  be  seen. 

Sulfates.  Use  BaCl2  instead  of  the  silver  nitrate.  If 
present,  the  insoluble  precipitate  of  BaSO4  will  be  seen. 


SECTION  XXIV 

SELECTED  EXERCISES 

An  Experiment  with  the  Albumen  of  Meat.  The  most 
important  solid  constituent  of  the  body  of  an  animal  is 
albumen.  Place  about  20  g.  of  lean  beef  finely  minced  in  a 
beaker  of  cold  water  and  gradually  heat  to  about  130°  F. 
Remove,  filter  the  liquid,  and  test  as  follows : 

To  a  portion  add  HNOg.  A  white  precipitate  or  a  decided 
milkiness  indicates  albumen. 

To  another  portion  add  a  few  drops  of  iodin.  A  yellow 
or  port-wine  color  indicates  the  presence  of  glycogeii  or 
animal  starch. 

Repeat  the  above  experiment  by  placing  the  same  weight 
of  beef  in  actively  boiling  water.  Leave  for  a  minute  and 
test  as  before.  How  do  you  account  for  the  difference  ? 
What  does  this  show  concerning  the  cooking  of  meats  ? 

Examination  of  Common  Salt.  Moisture.  Purchase  as 
many  different  brands  of  table  salt  as  possible ;  also  several 
samples  of  "  coarse-fine  "  and  rock  salt. 

Place  exactly  5  g.  of  the  sample  in  a  small  tared  Erlen- 
meyer  flask  and  heat  to  a  temperature  not  exceeding  150°  C. 
for  three  hours  011  a  sand  bath.  Remove  from  the  bath,  in- 
sert a  funnel  in  the  mouth  of  the  flask,  and  allow  the  contents 
to  cool.  The  introduction  of  the  funnel  renders  the  use  of  a 
desiccator  unnecessary  for  this  determination.  Reweigh,  and 
from  the  loss  of  weight  calculate  the  per  cent  of  moisture. 
Reserve  the  residue  for  the  determination  of  MgCl2. 

120 


SELECTED  EXERCISES  121 

Insoluble  Matter.  Dissolve  5  g.  of  the  sample  in  100  cc. 
of  water,  heating  gently  if  necessary.  Filter  the  solution 
through  a  balanced  filter  paper,  washing  the  residue  with 
warm  water  until  the  filtrate  shows  no  precipitate  with 
AgNO3  solution.  Dry  and  weigh  the  contents  of  the  filter 
paper  and  calculate  the  per  cent  of  insoluble  matter. 

Chlorin.  Dissolve  5  g.  of  the  undried  sample  in  a  little 
water  and  make  up  the  solution  to  exactly  500  cc.  in  a 
measuring  flask.  Mix  thoroughly  and  withdraw  10  cc.  by 
means  of  a  pipette.  Place  in  a  clean  beaker  and  add  an  equal 
volume  of  distilled  water.  Titrate  with  N/10  AgNO3,  using 
neutral  potassium  chromate  as  an  indicator  (see  p.  30).  A 
liter  of  N/10  silver  nitrate  contains  17g.  of  the  pure 
crystallized  salt. 

Deduct  0.1  cc.  of  the  silver  solution  added,  as  this  amount 
is  required  to  produce  the  permanent  red  tinge.  Every 
cubic  centimeter  of  the  N/10  AgNO3  is  equivalent  to 
0.00355  g.  of  chlorin. 

The  10  cc.  of  the  titrated  salt  solution  contained,  theo- 
retically, how  many  grams  of  chlorin  ?  How  many  grams 
did  you  find  ?  What  was  the  per  cent  of  chlorin  ? 

Suggestion.  How  many  grams  of  salt  did  you  dissolve  ? 
To  what  volume  did  you  dilute  it  ?  How  many  grams  of 
salt  in  10  cc.  of  this  solution  ? 

Calcium  Sulfate.  First  Method.  Dissolve  5  g.  of  the  sample 
in  20  cc.  of  water  to  which  2  cc.  of  HC1  have  been  added. 
Boil  gently,  being  careful  to  lose  none  of  the  solution  during 
the  process.  In  the  case  of  rock  salt  it  may  be  necessary  to 
continue  the  treatment  for  some  time  in  order  to  dissolve 
all  of  the  CaSO4. 

Neutralize  the  solution  with  ammonia  and  precipitate 
the  calcium  with  (NH4)2C2O4.  Allow  it  to  stand  overnight 


122         ELEMENTARY  APPLIED  CHEMISTRY 

and  filter  the  solution  through  a  fine,  ashless  filter  paper. 
Wash  the  residue  carefully,  dry,  and  ignite  it  in  a  weighed 
crucible  until  the  oxalate  is  converted  into  CaO.  This  will 
require  about  twenty  minutes  at  a  white  heat.  Cool  and 
weigh  as  CaO.  One  part  of  CaO  is  equivalent  to  2.4271 
parts  of  CaSO4.  Calculate  the  per  cent  of  CaSO8  in  the 
original  sample. 

Second  Method.  Dissolve  10  g.  of  salt  in  warm  water 
containing  1  per  cent  of  HC1.  Dilute  to  a  liter  and  draw 
out  250  cc.  (2.5  g.  of  salt).  Heat  this  portion  to  boiling, 
add  1  cc.  of  HC1,  and  immediately  pour  in  about  20  cc.  of 
boiling  10  per  cent  BaCl2.  Do  not  add  the  barium  chlorid 
solution  drop  by  drop,  but  introduce  it  all  at  once.  The 
precipitate  should  settle  in  half  an  hour.  Decant  the  clear 
portion  through  an  ashless  filter  paper.  Pour  100  cc.  of 
boiling  water  on  the  precipitate,  agitate,  and  allow  to  settle, 
which  it  should  do  in  about  four  minutes.  Decant  again 
and  repeat  the  operation  until  the  liquid  ceases  to  give 
an  acid  reaction.  Finally  wash  the  precipitate  on  the  filter. 
Dry,  ignite  at  a  low  heat,  and  weigh  the  BaSO4.  From  this 
calculate  the  per  cent  of  CaSO4  in  the  sample. 

Magnesium  Chlorid.  Into  the  flask  containing  the  dried 
residue  from  the  moisture  determination  place  25  cc.  of  abso- 
lute alcohol.  Cork  the  flask  and  gently  shake  the  contents 
from  time  to  time  for  ten  minutes.  Filter  and  evaporate 
the  alcohol,  which  contains  nothing  but  MgCl2.  Dissolve  the 
residue  in  water  and  titrate  with  N/10  AgNOg. 

From  the  chlorin  found  calculate  the  per  cent  of  MgCl2 
in  the  sample. 


WORKING  TABLE  OF  THE  ELEMENTS        123 


SYMBOLS,  ATOMIC  WEIGHTS,  AND  VALENCE  OF  THE 
MORE  IMPORTANT  ELEMENTS 


ELEMENT 

SYMBOL 

ATOMIC  WEIGHT 

VALENCE 

Aluminium         .... 

Al 

27.1 

3 

Antimony 

Sb 

120.2 

3,  5 

Arsenic     

As 

75 

3,  5 

Barium                .... 

Ba 

137.3 

2 

Bismuth 

Bi 

208 

3,  5 

Boron  .          

B 

11 

3 

Bromin          .     .          . 

Br 

79.9 

1 

Cadmium 

Cd 

112.4 

2 

Calcium    
Carbon                .... 

Ca 
C 

40 
12 

2 
4 

Chlorin 

Cl 

35.5 

1 

Chromium     
Cobalt  .          

Cr 

Co 

52.1 
58.9 

2,3,6 
2 

Copper      
Fluorin     ...... 
Gold               .          ... 

Cu 
F 
Au 

63.6 
19 
197.2 

1,2 
1 
1,  3 

Hydrogen 

H 

1 

1 

lodin    

I 

126.9 

1 

Iron 

Fe 

55.8 

2,  3 

Lead 

Pb 

207.1 

2,  4 

Magnesium    
Manganese 

Mg 
Mn 

24.3 
54.9 

2 
2,  4 

Mercury  
Nickel  

Hg 

Ni 

200 
58.6 

1,2 

2 

Nitrogen  ...... 
Oxv°"en 

N 

o 

14 

16 

3,5 

2 

Phosphorus  

p 

31 

3,  5 

Platinum  .... 

Pt 

195 

4 

Potassium 

K 

39.1 

1 

Silicon       

Si 

28.3 

4 

Silver  

As- 

107.8 

1 

Sodium     ...... 
Strontium 

Na 
Sr 

23 

87  6 

1 

2 

Sulfur  

S 

32 

2,  4,  6 

Tin.     .•    
Zinc     

Sn 
Zn 

119 
65.3 

2,4 

2 

INDEX 


Acetanilid,  detection  of,  102;  de- 
termination of,  104 
Acetic  acid,  per  cent  of,  22 
Acidity  of  milk,  20 
Acids  and  alkalis,  5 
Adulteration  of  milk,  45 
Albumen,  test  for,  118 
Alcohol,   ethyl,    55;    methyl,    60; 

per  cent  of,  58 ;  preparation  of, 

56 ;  tables,  66 
Alkali,  free  and  combined  in  soap, 

25 

Alkaline  carbonates  in  soap,  26 
Alum;  tests  for,  39 
Ammonia  in  baking  powder,  39; 

in  water,  detection  of,  31 
Ammonium    molybdate    solution, 

33 

Annatto,  detection  of,  45 
Arsenic,  tests  for,  107 
Artificial  colors  in  milk,  45 
Ash,  of  cereal  products,  116;    of 

vinegar,  22 
Atomic  weights,  table  of,  123 

Bach's  table  for  oil,  111 
Baking-powder  analysis,  35 
Baking  soda,  test  for  purity,  20; 

in  milk,  47 

Barium  sulfate  in  paint,  110 
Bases  in  baking  powder,  39 
Borates  in  soap,  27 
Boric  acid,  detection  of,  91 
Boron  in  milk,  47 


Butter,  boron  compounds  in,  92; 
coal-tar  dye  in,  77 ;  renovated,  to 
distinguish,  112 

Calcium  carbonate  in  soils,  9 
Calcium  sucrate  in  cream,  48 
Calcium  sulfate  in  salt,  121 
Cane  sugar,  inversion  of,  98 
Caramel,  detection  of,  79 
Carbohydrates  in  cereal  products, 

117 

Carbon  dioxid  in  baking  powders, 35 
Cheese,  fat  in,  52 
Chlorids  in  plants,  15 
Chlorin,   in    salt,   121  ;    in  water, 

tests  for,  30 

Chlorophyl,  extraction  of,  13 
Cider  vinegar,  to  distinguish,  23 
Citric  acid,  per  cent  of,  19 
Cloth,  arsenic  in,  106 
Coal-tar  dye,  detection  of,  76 
Cochineal,  80 
Cocoa,  purity  of,  24 
Condensed  milk,  fat  in,  53 ;  times 

condensed,  53 

Cottonseed  oil  in  olive  oil,  111 
Cream,  determination  of  fat  in,  52 

Dirt  in  milk,  44 
Distillation  experiments,  54 

Equivalents  of  N/10  NaOH,  19 
Erythrosin  as  an  indicator,  34 
Essential  oils,  extraction  of,  44 


.125 


126         ELEMENTARY  APPLIED  CHEMISTRY 


Fabrics,  wool  and  cotton  in,  7 
Fat,  in   cereal   products,   116;    in 

milk  by  the  Babcock  test,  41 
Fatty  acids  in  olive  oil,  110 
Fehling's  solution,  98 
Filtration  experiments,  1 
Flame  tests,  10 
Food  preservatives,  90 
Food  values,  determination  of,  113 
Formaldehyde  in  milk,  46 
Fuel  values,  calories,  117 

Gelatin  in  milk,  cream,  etc.,  48 
Glucose,  preparation  of,  97;   tests 

for,  98 
Gunning's   method    for    nitrogen, 

115 
Gunpowder,  analysis  of,  2 

Hardness  of  water,  34 
Headache  powders,  analysis  of,  102 
Honey,  glucose  in,  99 
Hydrochloric  acid  in  soils,  10 

Ice  cream,  fat  in,  52  ;  gelatin  in, 
48  ;  starch  in,  52 

Ink  eradicator,  88 

Invert  sugar,  in  honey,  99  ;  in  veg- 
etables, 100 

Iron  in  plants,  15 

Iron  oxid  in  soils,  9 

Lactic  acid,  per  cent  of,  20 

Lead  in  paint,  110 

Lemon  extract,  coal-tar  dye  in,  78 ; 
per  cent  of  oil  in,  65;  prepara- 
tion of,  64 

Lime  in  paint,  110 

Litmus,  use  of,  5 

Magnesium  in  soils,  11 ;  chlorid  in 
salt,  122 


Maple  sirup,  tests  for  purity,  100 

Martin's  reagent,  78 

Metallic  compounds  in  water,  34 

Methyl  orange  as  an  indicator,  34 

Milk  analysis,  41 

Mineral  acids  in  vinegar,  23 

Nessler's  reagent,  31 
Nitrate  of  mercury,  acid,  49 
Nitrates  and  nitrites,  detection  of, 

in  water,  32 
Nitric  aeid  in  soils,  11 
Nitrogen,  determination   of,    115 ; 

in  plants,  13 

Oil,  extraction  of,  from  paint,  109  ; 

olive,  examination  of,  110 
Oleomargarine,  to  detect,  112 
Oxalic  acid  N/10,  17 
Oxygen  absorbed  in  water,  33 
Oysters,  water  in,  4 

Paint  analysis,  109 
Phenolphthalein  as  an  indicator,  17 
Phosphates  in  water,  32 
Phosphoric  acid,  in  plants,  15;  in 

soils,  11 

Plant  analysis,  13 
Potash,  in  plants,  14 ;  in  soils,  10 
Potassium  sulfo-cyanide  test,  10 
Preservatives  in  milk,  46 
Proteins,  determination  of,  115 
Pumice  stone  in  tooth  powder,  95 

Radicals  in  baking  powder,  38 
Raffia  dyeing,  81 

Richmond  scale  for  total  solids  in 
milk,  44 

Saccharin,  detection  of,  94 
Salicylic  acid,  detection  of,  93 
Salt  analysis,  120 


INDEX 


127 


Sand  in  soils,  11 

Sediment  in  water,  28 

Silica  in  plants,  15 

Skimmed  milk,  identification  of,  51 

Soap,  analysis  of,  25 ;  insoluble  mat- 
ter in,  25 

Soda,  in  plants,  14 ;  in  soils,  10 

Sodium  bicarbonate  in  milk,  47 

Sodium  hydrate  N/10,  17 

Soil  analysis,  9 

Soils,  acidity  and  alkalinity  of,  24 

Specific  gravity  of  milk,  43 

Stains,  chemistry  of,  88 

Standard  solutions,  16 ;  exercises 
with,  19 

Starch,  conversion  to  invert  sugar, 
97 ;  effect  of  mastication  on, 
100 ;  test  for,  14 

Sugar  in  urine,  detection  of,  119 

Sulfates,  in  plants,  15  ;  in  soils,  10 

Sulf  uric  acid,  in  soils,  10 ;  in  vine- 
gar, 23 

Sulfurous  acid,  detection  of,  90; 
determination  of,  91 

Tartrates,  test  for,  38 
Tea,  soluble  matter  in,  3 


Theine,  extraction  of,  4 

Titration,  16 

Tonsillitis  Specific,  1 

Tooth  powder,  examination  of,  95 

Total  solids,  in  milk,  43 ;  in  water, 

29 

Turmeric,  tests  for,  80 
Turmeric  tincture,  preparation  of, 

47 

Urine  analysis,  118 

Vanilla  extract,  preparation  of,  62 ; 

tests  for,  63 
Vegetable  colors,  identification  of, 

79 

Vinegar  analysis,  21 
Vinegar  eels,  21 

Wall  paper,  arsenic  in, -106 

Water,  analysis  of,  28;  in  cereal 
products,  116 ;  in  milk,  detec- 
tion of,  51 

Waterhouse  test  for  butter,  112 

Wool  in  fabrics,  7 

Zinc  in  paint,  detection  of,  110 


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